Building Your Pond

In This Chapter
  • Selecting the best construction method for you
  • Changing swimmers: When a pool becomes a pond
  • Minding the material
  • Constructing a pond with a liner
  • Opting for a concrete wall with a liner
  • Adding other essentials along with some bells and whistles
  • Aging the pond
If you want to build a koi pond in your yard, you have many decisions to make. The first and foremost decision: Are you going to build this pond yourself or hire a professional to do it for you? If you’re considering hiring a contractor to do the dirty work, you want to make sure you find one who knows his stuff (more on that later in this chapter).

After you decide on the builder, you need to figure out which type of pond you want to build because the type of pond greatly affects the types of building materials you choose. But where to start? (If you haven’t read Chapter Planning Your Koi Pond, you may want to check it out now to get the big picture on planning.)

Don’t worry. Take your time and try to enjoy the process. This chapter reviews some of the more common construction methods and gives you the good and bad points of each type. We also walk you through the three different types of pond constructions: with a liner, with a liner and concrete-block walls, or simply with concrete blocks.

This chapter also tells you how to complete the pond with a filter system, lighting, skimmers, and other components. Finally, we help you avoid problems as your new pond settles in.

Who Will Dig (And Build) Your Pond?


Building a pond isn’t a decision to be taken lightly. Your first major step is to make the all-important decision of whether to build the pond yourself or hire a professional contractor.
Tip
If this is your first koi pond, discuss your plans with other koi fanciers before you turn a single shovelful of dirt or call a single contractor. This move will save you a lot of grief. Other koi keepers are very willing to share their been there, done that experiences.
This section covers the pros and cons of building the pond yourself compared to hiring a professional. If you do decide to hire a professional, this section helps you ask the right questions.

Doing it yourself


If you have the skills, you can certainly dig and build your own pond. You may need a few friends to help because it’s definitely hard work.

Knowing what you’re getting yourself into


Digging and building your own pond is physically hard work. You have to deal with many issues and situations, including:
- Lifting the (heavy) dirt: One of the first problems is how to lift the dirt out of the future pond area without crushing one of the dirt sides. If you do decide to go this route, you can create a ledge to help keep the sides from crushing — see Figure 7-1.
- Removing the dirt: After you dig the dirt from the pond, what are you going to do with it? You’ll have way too much to scatter into your lawn or dump into raised flower beds; you’d have the only 7-foot chrysanthemum bed in town!
You may be able to run a classified ad offering free dirt and find someone who can use it. As a last resort, you can haul off the dirt and dump it in a landfill — for a fee.
- Digging trenches for the filter pipes and (maybe) a site for the filter: You’ll need to dig trenches for the filter pipes, and a pit for the pump (for an above-ground filtration system) or a larger pit to contain the filter and pump (for a gravity-fed system). All of the pits will need to be brick or cement block lined, to avoid cave-ins and for access.
- Walling in the pond: You can use a liner, or go for the more solid approach of concrete blocks.
- Finishing the pond edge: You’ll be adding capstones or a raised lip at the edge of the pond.
- Installing and hooking up the filter system: This is where the rubber will meet the road for the success of your pond.
At this point we can understand if the idea of building your own pond is beginning to sound less like fun and more like work.

Figure 7-1: Creating a step while digging to avoid crushing the pond’s sides.

Hiring workers to help with the dirty work


Hiring out the digging may help. You can hire someone with a backhoe and include dirt disposal as part of the deal. That part of the task is then done, quite likely in less time than it would have taken you and three of your best friends — or ex-best friends.

Even if you do take on the actual construction of your pond, you may want to hire out parts of the job. This includes a fiberglass installer or a pump service that gets your ready-mix concrete into your backyard, or a masseur who makes house calls.

Hiring a professional for the entire project


You may decide to hire a koi pond construction firm to handle the entire project. With this arrangement, you’re involved in the site selection and pond design. The contractor does the rest. The cost of your pond increases with the more experts you bring onboard. But money well spent at this point can save you dollars and huge headaches down the road. Remember, you only have to do it right once . . . until you want a larger pond.


Finding a reputable contractor


If you decide to hire out the construction of the entire pond, make sure you find a reputable contractor. Ask the following people for advice:
- Your koi friends: Ask them about contractors they can recommend and about construction issues that have come up in their own pond projects.
- Folks you find in the phone book or online: Set up your own query system. Look in the yellow pages of your phone book. Go online and type in pond contractors and your zip code. Ask your friends and neighbors if they know of any pond contractors, or if they know of someone who might know of a contractor.

Asking the right questions


To find out whether a contractor is the right one, start with the right questions. You can discover a lot about the prospective contractors with these questions:
- How many koi ponds have you built? Ask specifically about past projects. Individuals who build garden ponds or swimming pools may not know how a koi pond is different, and you need to find this out. A koi pond requires a different drainage system, filtration system, and pump than a garden pond or a swimming pool (check out Chapter Planning Your Koi Pondfor more information on these essentials). A builder who assures you that “3 feet is plenty deep enough” is not going to be the builder of your dreams.
- How many years have you been building koi ponds? If he hesitates and does that sideways-shift-of-the-eyes thing, brace yourself. This guy knows koi ponds like you know early Sanskrit.
- Are you comfortable telling me about problems you’ve had in building koi ponds? An honest construction person, one who is comfortable with his (or her) own abilities may start to laugh at this question, and then proceed to tell you about the huge rocks in the excavation site, the early snowfall/enormous rainstorm, or the middle-of-the-project design changes. Understand that unavoidable/unforeseen problems will increase the cost of a pond, so keep some money available for these problems.
Remember
- Can you provide references from previous koi pond projects? Make sure you check these references! Talk to people whose ponds were built by each contractor and go look at the ponds. Ask about problems with pea soup syndrome or other water-quality issues (see Chapter Maintaining Your Pond for more on these questions).

Closing the deal


After you’ve chosen one particular contractor, make sure you finalize all the details before you sign the contract. Yes, these are points that the builder and potential pond owner need to agree will be factored into the design.
They include:
_ The koi pond must have at least one bottom drain for every 16 square feet of bottom area, and the floor of the pond must be tilted down toward the drains. The tilt ensures detritus that falls to the floor of the pond will be channeled towards the drains and into the filtration system.
- The pond must not have a gravel, rock, or sand flooring. It must have solid, smooth flooring, so there’s no spaces for anaerobic bacteria to hide, and so the suction from the filter can pull waste into the drains.
- The pond must have vertical walls with a minimum depth of 4 feet, so the koi can escape predators and for better water temperature control.
- An external pump is the only sane choice. Pumps stop working, and no one relishes the idea of jumping into a koi pond, grabbing a nonworking pump, and lifting it out of the pond (you did turn off the electricity before you jumped in, didn’t you?). Pumps last maybe three years, and the financial side of replacing them is painful enough.
Remember
You may want to add a clause that holds back the final 10 percent until the pond is operating according to mutually agreed-upon guidelines.

Converting a Swimming Pool into a Koi Pond


If you already own a swimming pool and find you aren’t using it much these days, you may be glad to know you can easily revamp it, for not a whole lot of money, into a terrific koi pond. This is the route lots of koi-keepers tend to take.

In order to convert your swimming pool into a koi pond, you need to take the following steps, more or less in the order given:
1. Drain the pool and remove the ladders.
Use waterproof patching putty to fill the holes left by the screws.
2. Round all corners in the pool.
Doing so prevents dead areas of no water circulation and prevents detritus from lining the bottom perimeter of the pond. To round the corners:
Add a baffle at a 45-degree angle at each vertical corner.
You can use bricks, stacking them on top of each other (see Figure 7-2a). You can also use 1-x-12 boards laid upright against the corners and secured in place with those big blue cement screws (see Figure 7-2b). Waterproof the boards with a thin layer of cement.
Add a smaller 45-degree baffle (made from cement) between the bottom perimeter of the pool and the sides.
3. Change the filtration system and install larger drainpipes.
A swimming-pool filter is a high head (meaning high pressure and strong pump), low volume system. A swimming-pool filter can take eight hours to circulate the entire pool, which tells you something about the water quality in the average swimming pool. A good koi-pond filter should circulate the pond capacity every two hours. 

Figure 7-2: Rounding the corners of a pool. 
Tip
4. Change out the drainpipes for 4-inch-diameter pipes.
You’ll also want to change out the drain units for domed drains that can incorporate aeration.
Changing the drainpipes means literally chipping in a new trench for each drain, through the bottom of the pond, in a line from the filter to the drain. There’s no sense in removing the old drainpipes — they may be sealed in place by cement. Place the new PVC pipes into the new trenches. Dig a trench on the outside of the pond, next to the wall, so you can connect the plumbing to the filter on the far end.
5. Add a raised lip to the edge of the pool to avoid groundwater intrusion. This includes any kind of runoff water., no matter what the source. (See Figure 7-3 for an illustration of the components of a raised lip.)
6. Paint the pool a dark color with an epoxy-like pool liner.
You want to paint your empty pool for two reasons: You want people to notice your new koi pond and not say, “Oh, you’ve put fish (pause) in your swimming pool (with lowered eyebrows and a sideways glance from narrowed eyes).” Also, you need to seal the cement (and umpteen years of chemicals) away from your fish.
 
Figure 7-3: A raised lip.
Tip
Buy a paint-on or spray-on epoxy paint that’s made just for this purpose. You want a product that seals off the cement and has a bit of flexibility so it can serve as a liner, preventing tiny tile and cement cracks from becoming a problem. This is pretty much a specialized product, meaning you will not find it at a paint store or at a home improvement store. Go online and type epoxy pond liner and sealer — one brand is called Pond Armor.

Selecting the Building Materials for Your Spanking New Pond


A basic koi pond must be at least 4 feet deep and about 6 feet wide x 9 feet long to afford the minimum swimming area for your growing koi. This size pond holds just over 1,500 gallons (and this is considered a small pond!). Experienced koi experts say a 3,000-gallon pond is as easy to keep as a 1,500-gallon one, but a smaller pond is a lot less intimidating for a beginner. It’s also less expensive to build.

Whether you’re building a liner-alone pond, a concrete pond, or a concrete and liner pond (check out Chapter Planning Your Koi Pond for more general info on these three types of ponds), ensure that it’s appropriate for your new koi by choosing the right building materials.

First, keep in mind the following general points regarding materials, no matter what type of pond you choose:
- The materials used for the pond must be watertight and nontoxic to fish.
- The materials must be long lasting; liners are guaranteed for 20 years, and concrete ponds, like diamonds, are forever.
- The surface of the pond needs to be even and smooth, so detritus and bacteria can’t find a refuge.
To get started, noted that all three pond types need the following general materials:
- Large-enough diameter drains and PVC pipes, which bring the water from the pond into the filter.
- A filter outflow, which takes the filtered water back into the pond.
- A filter and pump, connected inline to the drainpipes and the filter outflow in the pond (depending on the type of filter, the pump is between the filter and the pond or between the filter and the outflow).
The following supplies are specific to a liner-alone pond:
- You’ll need a liner, one large enough to line the entire pond with at least an 18-inch overlap at ground level.
- The pond dimensions will stay more constant if the liner is, in effect, suspended from a concrete collar or ring at ground level. The collar will take concrete and rebar.
- You’ll need bulkheads for each drain, light, and skimmer that goes through the liner. These bulkheads seal the openings, so no water can ooze through the openings. Water under pressure can be pretty sneaky, working its way into areas you thought would be no problem at all, so a bulkhead is a must for any opening.
You need the following materials for a concrete/cement block pond:
- Enough concrete for the floor, and enough concrete or concrete and cement blocks for the walls
- Rebar for the flooring and walls, to strengthen the concrete The following supplies are specific to a concrete and liner pond:
- Concrete and rebar for the collar, walls, and floor
- A liner large enough to line the pond and for an 18-inch rim once the liner is in place

Going with a Liner-Alone Pond


Several types of liners are available in the marketplace, and even the best liners are inexpensive. Look for a liner that is 45 or 60 mils thick. For a small 9-x-6-x-4-foot koi pond, a 45-mil liner costs about $170; a 60-mil liner costs about $285 (“mil,” in this case, means thousandths of an inch).
Warning!
Liners alone work for small ponds 4 feet deep x 6 feet x 9 feet (which is our suggested minimum). The deeper the pond excavation, the greater the chance that the sides will collapse inwards of their own volition as the pond is dug or as the pond fills with water.

Starting with a pond wall ring


You can reduce the chance of a wall collapse and still use a liner for a bigger pond by installing a pond wall ring — also called a pond collar — before you begin digging the pond itself. The pond wall ring is a solid concrete footer (a concrete base that will support a larger heavier structure above it or hanging from it) at the top edge of the pond. The liner is suspended from this ring.
To put in a pond wall ring, take the following steps:
1. Stake out the shape and dimensions of your pond.
2. Dig a trench about a foot wide and 10 inches deep at the outside edge of your soon-to-be pond, all the way around your pond.
The actual dimensions of the ring depend on the type of soil you have. (Sand and heavy clay soils require a wider and deeper ring, up to 15 inches wide and 10 inches deep, with rebar added.) This trench becomes your pond wall ring.
3. Line the pond-side of the trench with 1 x 8s or with 8-inch-wide strips of oiled plywood.
Take care to stake the wood so the interior edge of the ring will stay vertical when you pour concrete into the trench.
4. Add wire braces and rebar to the pond ring trench, with at least two (and preferably three) lengths of rebar throughout the trench.
The rebar sits atop the wire braces and ends up in the center of the poured concrete.
5. Pour or pump the concrete into the pond ring to a depth of 6 inches (10 inches for clay soils, which are notoriously slippery).
Tip
Figuring out how much concrete you need isn’t difficult. A yard of concrete contains 9 cubic feet. Each linear foot of your 12-inch-wide, 6-inch-deep trench takes 1⁄2 cubic foot (6 x 12 x 12 inches), so 18 feet of trench requires 1 cubic yard of concrete.
6. Wait about half an hour and use a float (a rectangular trowel, used as a smoothing device) to smooth the top surface.
Use an edging tool to round the pond-side edge of the concrete so the edge won’t cut or pierce the liner when you install it and pull it up over the edge of the pond ring.
7. Tamp the poured concrete to collapse any air pockets. Let it set up for 24 to 36 hours before removing the wood.
Let the concrete cure for another 36 hours.
At this point, the pond wall ring is about 4 inches below ground surface. Later you’ll secure the liner’s top edge to this ring and then mortar bricks or concrete blocks on top to create the pond edge.

Excavating and adding the drains


After the pond ring has hardened, you can begin the real fun — digging. You can dig by hand or with a small backhoe.

Drains may seem like a pain to install, but they are a vital part of the system of keeping your pond clean. A good drainage system, coupled with a good filter, means your pond will stay clean with comparatively little work on your part.

Digging trenches for the drainpipes and the drains themselves only has to be done once, if you do it right — when else can you get such a payoff?

After you remove the dirt from the pond drain trenches, take the following steps:
1. Use a round-tipped shovel to round all corners in the pond (at the sides and at the bottom).
Use the rounded tip of the shovel to scrape the corners round and remove the scrapings. Rounding the corners makes it easier for the filter returns to set up a circular current in the pond. This helps keep the pond clean., and it also provides a current for the fish to swim against, a bit like those narrow swimming pools that have a strong current to make swimming more work.
2. Build a wooden bridge across the width of the pond and extend it about 3 feet beyond the edge of the pond at both ends.
This bridge becomes your safe access to the pond, enabling you to place the drains and the filter return — and remove any extra dirt — without clambering in and out over the edge.
3. Place the bottom drains.
Center the drain(s) along the long measurement of your pond, each with a 4-foot radius. The filter system in a koi pond is designed to pull detritus in from a 4-foot circle around each drain. That’s why you locate the drains at 8-foot intervals.
4. Once the filters and drains, are in place, add dirt to the floor, starting at the perimeter and working towards the drains.
Your goal is to slant the bottom of the pond towards the drains 2 to 6 inches per foot.
5. Add the filter outflow, the pipes that will take clean water from the filter back into the pond.
Filter outflows can be positioned in several ways. You can send all or part of it through a bog pond next to the koi pond and let it drip from the bog pond into the koi pond. You’ll need a big bog pond to effectively treat 750 gallons an hour, or whatever your hourly pump flow might be. To send only part of the filter outflow through a bog pond, use a Y-shaped PVC joint in the filter outflow, and send half to the bog and the other half directly into the pond or into a waterfall that feeds the pond.
To use the full force of the filter outflow to create current in your koi pond, dig carefully under the pond collar and bring the filter outflow into the pond in a corner, right through the 45-degree baffle you put in place (you’ll seal around the pipe with Silastic, or you can buy one-piece outflow pipes that are cast with the mounting plate in place). You can add joints in the PVC piping to create one high and one low outflow. 
For a large pond, you can set up two filters, each handling two or more drains and returning the water to the pond via corner outflows as described above, but in opposite corners and directed in opposite directions.
Remember
Make sure you dig carefully. With a liner, the fewer bulkheads through the liner, the fewer leaks now and in the future.

Inserting the liner


If you’ve read the preceeding sections and followed the steps, you’ve dug your hole, removed most of the dirt, added your drains, and slanted the bottom of your pond. Now you need to insert the liner. Take these steps:
1. Add a cushion to the bottom of your pond to prevent tree roots from puncturing the liner.
Remember
A liner doesn’t have much give when it’s held against the earth by 1,500 gallons of water. (That’s almost 12,500 pounds!) You need to provident some kind of shield to protect the liner. Install a liner underlayment that’s made for this purpose. Cost is about $2.25 a square yard.
2. Trim the underlayment around the drains. As you place the underlayment, take care not to step on or trip over the drains. Cut an X over each drain so you can push the underlayment down over the drain; then trim the points off or tuck them under.
3. Unfold the liner and slide it over the pond opening.
Allow the liner to drape down into the pond.
4. Hold the liner so it sags into the pond, but adjust its position so it overlaps the pond on all four sides by about 18 inches.
Remember
Let the liner flow down into the pond and keep the edges of the liner out of the pond. You generally need three or four people to help with this step because the liner is big and heavy. You want to stay back from the edge of the pond because you don’t want to break the edge of the collar or crumble the side of the pond.
5. After the liner is lowered into the center of the pond, select one person to get into the pond to arrange the liner as it moves down.
This person flattens the folds so the liner lies as flat as possible, while the people above him or her pull and loosen the liner as directed.
6. The person in the pond is the one who will pull the liner taut over the bottom drains and cut the lining for the bulkhead installation over the drains.
Start with a simple “X” in the center of the drain, for positioning of the bulkhead, and then trim off the corners to create a permanent opening in the liner. Screw the bulkhead in place, making certain that the liner is between the two components all the way around the drain. Many people add a rim of sealant such as Silastic before they attach the bulkhead to the drain.
After you’ve cut and installed the liner around the bottom drains, only minor shifting is now possible. This is where you’ll tidy the folds in the corners of the pond, and stretch the liner out over the edge of the pond opening.
7. Once the liner has been linked to the bottom drains, you can begin adding water to the pond, continuing to adjust folds of the liner to create as few deep folds as possible.
Deeper folds become havens for anaerobic bacteria, so go for shallow pleats rather than deep folds.
8. You can install a skimmer at the surface of the water.
Skimmers can be protein skimmers, to take in and filter out surface foam, or they can be surface skimmers, that take in leaves and other solid-surface debris. Either one replaces what you’d do with a long-handled skimmer; the protein skimmer is specifically designed to dispose of surface foam.
Where and how the skimmer is fastened to the pond wall depends on the design of the skimmer. Surface skimmers need to be mounted so the water level hits at the middle of the intake; protein skimmers need to be mounted so the opening is at water level. In either case, with a pond liner, a rigid backing needs to be in place behind the liner so the skimmer can be fastened via a bulkhead to the brace behind the liner.
9. Pull the liner up over the edge of the pond ring. Using washers and masonry screws, pin the liner in place atop the pond ring.
10. Add brick or concrete blocks to the upper edge of the pond, atop the pond ring and liner.
The top layer of bricks or blocks is called the capstone, and its upper edge should be at least 6 inches above ground level to keep rainwater runoff out of your pond.

Creating a Pond with a Liner and Concrete-Block Walls


For many koi fanciers, the pool of choice has a pond liner that’s propped up by rigid, concrete-block walls. This version combines some of the economies of the pond liner with the do-it-once-and-forget-it appeal of concrete block. It also permits you to build a sizeable pond for not a lot of money.

Shoveling dirt: Dig time


You begin this pond by digging. Depending on how much work you want to do, you can dig the pond yourself (a lot of work) or with some strong friends (less work, a lot more fun), or you can hire a backhoe operator with a small backhoe. If you want to dig the pond yourself, follow these steps:
1. Lay out a garden hose on the ground to create your roughly oval or roughly rectangular pond shape or stake out your pond shape and size.
You’ll build your pond inside these lines.
2. Start digging.
Create a ramp at one end of the pond so you can remove the dirt via a wheelbarrow (you’ll need to fill in and tamp down that end of the pond when you finish the excavation), or let the backhoe do the labor.
3. After the pond has been excavated, the first concrete work will be for a footer that will underlie the walls of the pond.
This is much like the pond ring used for the liner-alone pond, but this time, it will be at the bottom of an excavation, not next to it. The footer is poured into a trench around the perimeter down inside the pond. Stakes, string, and a level can help you dig an even trench.
Remember
The footer’s depth and width depends on your soil type. The footer must bear the weight of the walls and the pressure of the water. At a minimum, the footer needs to be 12 inches wide and about 8 inches deep. Your concrete supplier can tell you what sort of soil you have in your area and may suggest the dimensions of your footer.
4. Add wire braces every 2 feet or so along the footer trench.
5. Place the rebar atop the wire braces, so when the concrete is poured, the rebar will be in the center of the concrete.
Place at least two lengths of rebar and preferably three throughout the trench. The rebar gives extra strength to the footer.
6. Buy ready-mixed concrete; when the truck delivers it, wheelbarrow it from the street to your pond site.
Your cost will be about $100 per cubic yard. You can also mix the concrete yourself, using a small concrete mixer. These rent for about $100 a day.
7. Pour the concrete into the footer at the bottom of the pond excavation, and move it into the far reaches of the footer with a concrete hoe. Use a float to smooth the concrete and a 2-foot level to make certain the top surface of the footer is essentially level.
Having a level footer makes it easier to place level layers of concrete block. After you’ve troweled or floated the upper surface smooth, you’re done — for 24 hours.
8. Allow the concrete to cure for one day.
Laying the block walls
Remember
Even if you’ve never laid block before, you can lay your own concrete block (as long as you keep your pond size modest). Just remember two important caveats about using concrete:
It’s hard work. The blocks weigh 40 pounds each. You may not want to do this by yourself — sharing the workload is a good idea.
- It’s not cheap. The blocks can be expensive. And even though laying your own concrete block is less expensive than hiring a pro, you don’t want to make any costly mistakes. If you hire a professional(s) to lay the block and the walls come out wavy, you’re not the one who has to fix it. (And yes, knocking apart concrete blocks is harder than concreting them together.)
After you let the footer cure for a day (see the previous section), you’re ready to start laying the wall. Stick to these steps:
1. Use stakes and string to keep your blocks straight.
2. Lay the first layer of block on their sides, with the block openings facing into the pond.
Your filter intake pipes will thread through these openings without any extra work on your part.
3. Locate the filter as close as possible to the drain locations.
In koi-pond plumbing, the shortest, straightest plumbed path is always the most beautiful.
4. Use your level to keep the block rows even as you build the walls, tamping the blocks with the heel of your hand or the end of your trowel to settle each into alignment.
5. Lock the corners of the pond with alternating blocks from each side, just as you’ve seen concrete-block houses built.
6. Round the corners with bricks or wooden brace (See Figure 7-2).
7. To increase the strength of the walls, insert rebar down into the walls as the layers of concrete block build up. Then pump concrete down into the walls to create a solid concrete wall.
8. Keep laying the block until the upper edge is about 3 inches above ground level. Stop here; you won’t lay more block until the plumbing and liner are in place.
After the plumbing and the liner are in place, you’ll finish the cement work on your pond. For ponds that are almost at ground level, you’ll add a layer of capstones — flat cement blocks or cement bricks without openings atop the final level of cement blocks — and pull the liner over this solid layer. You’ll use washers and cement screws to hold the liner in place toward the outside edge of this stone layer. Then you’ll add another layer of capstone, concealing the liner between the layers.

For ponds that are built up from the ground’s surface, perhaps to create a seating edge along the entire perimeter of the pond, or if there are restrictions on how deep a pond can be dug, be certain that your liner will be large enough to reach from the bottom of the pond, up the walls of the pond, to the far edge of the first layer of capstones.
Remember
You may need to shore up the walls within the pond pit temporarily with plywood sheets braced with 2 x 4s pounded into the dirt on the floor of the pond for a day or so until the concrete sets.

Aligning the drains


Once the footer and the walls are in place, you’re ready to add the bottom drains, but before you begin this phase, you’ll be working outside of the pond, installing the plumbing for the filter.
1. Dig a trench from the pond edge (at the approximate location of each drain) to the filter installation point.
Complete this step a day or two after you lay the bricks, just before you remove the wall braces.
2. Run a length of 3- or 4-inch PVC pipe along each trench.
These pipes will pull water from each drain to the filter.
3. Backfill the walls of the trench with gravel or sand from the excavation, tamping it into place as you add it.
You may need to buy gravel or a load of sand if your soil is clay; clay soils can’t be used for backfill because they’re inherently slippery.
4. Place the filter drains in the pond floor, equidistant from each other and the sides of the pond and near the external drainpipes you just added.
Four- or six-inch drains work well. Because the filter drain units are about a foot high, you’ll have to dig down into the dirt floor of the pond to bury the lower 6 inches of the drain unit. Add drain pipes between the drains and the nearest external drainpipe.
5. As soon as the drainpipes are hooked up, add dirt to the pond bottom until you have a slanted floor, slanting down to the drains at a rate of 2 to 6 inches per foot.
When you’ve completed this step, only the round drain unit top will be exposed. 

Adding the liner


Now you’re ready to add the liner underlayment, the liner. You’ll secure the liner with cement screws and washers and add another layer of capstones . The steps are the same as in a liner-alone pool. Check out “Inserting the liner” earlier in this chapter for the basics about these steps.

The all-concrete-block pond


The all-concrete-block pond uses the same steps as the pond liner with concrete-block walls with two exceptions:
- The bottom of this pond is poured concrete.
- The liner is replaced by a paint-on or spray-on coating that seals the block and mortar.
Tip
It’s possible to build the components of this pond in different orders. The design we describe starts with the hole in the ground and then adds the footer for the walls, the filter outflows, the walls, the bottom drains, and finally the concrete bottom. Other designs will start with a pond excavation, but then will add a poured-concrete bottom then add the walls, install the bottom drains, and finally add a second layer of concrete on the pond bottom.
Base your design in part on
- Your type of soil
- The height of your water table
- How much of your pond will extend above the surface of the ground
Discuss these variables with other individuals who have built koi ponds in your area, a professional pond builder, or even a structural engineer. Note: Altering plans before you begin to build is really dirt cheap.

To build an all-concrete pond, follow the steps for the liner-with-concrete-block-walls pond (check out “Creating a Pond with a Liner and Concrete-Block Walls” earlier in this chapter) until the walls are installed and you’re ready to place the drains. When you reach that point, follow these steps:

1. Rake the dirt on the bottom until you have the 2- to 6-inch per foot slant toward the center of the pond; then place the drains along the central depression.
2. Bury each drain until only 6 inches is above ground level; add a trench from the base of the drain to the nearest external drainpipe.
3. Cut a length of 3- or 4-inch PVC pipe to fit between each drain and its corresponding external drainpipe; then place the pipes in the trenches.
4. Connect the pipes with the drain on one end and the external drainpipe on the other.
5. Fill the trenches with dirt, add the wire braces and rebar at regular intervals along the pond floor, and order the concrete for the pond floor.
This last step doesn’t take a great deal of concrete; a 6-inch-thick floor for a 6-x-9-foot pond only takes 1 cubic yard.
6. Space out the concrete on the pond floor as you dump each bucket.
This timesaver places the concrete in an almost even layer, thereby minimizing your effort to spread the concrete across the pond floor.
7. Run a bevel between the sides and the pond floor as you trowel the concrete into place on the pond floor, to eliminate the usual 90-degree angle between floor and walls, where debris will collect.
8. Let the concrete floor cure for a day before you walk on it.
9. Once the concrete has cured for a day or two, you’ll need to seal it, just as you’d seal the concrete walls of a converted swimming pool. (Concrete is extremely alkaline, and it will affect your water chemistry for years unless you seal it.)
These sealers are not products you can buy at a home improvement stores. They are nontoxic epoxy coatings that you spray, brush or roll on. They are most easily purchased online. The manufacturer may list retail outlets that sell the product, but you have to go online to find the name of the retailer.

Identifying (And Adding) Other Construction Components


Now that you have the pond shell, what’s next? You need to install a filter, but is there anything else you really ought to consider? But of course — and Figure 7-4 gives you a quick preview of some of the various components, which we explain in this section.


Figure 7-4: A schematic of a completed outdoor pond.

Installing the filtration unit


Chapter Planning Your Koi Pond discusses the two main options you have when adding a filtration unit to your pond. If you decide to go with an aboveground filter, you need a second trench for the filter outflow. The outflow pipe can be plumbed to
- A small waterfall that trickles into the pond
- A bog garden that empties into the pond
- Returns that you install in the pond corners
If you go with a gravity-fed filter, you need one trench for the PVC pipe that connects the external drainpipes to the first filter unit and another trench for the outflow pipe from the water pump. Like the above-ground filters, the water from the outflow can enter the pond through a waterfall, a bog garden, or outflow pipes in the pond corners.
Tip
Pick a site for your gravity-fed filters adjacent to the pond but not in your line of vision of the pond. Granted, the pond filter area is covered, but when you place it on one side or the other, you’re not forced to look at it every time you look at the pond.
Whether you have an above-ground filter or a gravity-fed filter, we offer these guidelines:
- For obvious reasons, be sure you buy a water pump or water pumps powerful enough to do the task. Your pump(s) should have an hourly rate equal to half the capacity of your pond.
- Use sweep bends in the PVC pipes rather than right-angle turns to reduce what an aerodynamicist would call the coefficient of drag. You don’t want to slow down the speed of the water in the pipes, for either type of filter.
For the gravity-fed filter with the pump after the filter, you’re paying big bucks for water ejected from the pump at a comparatively high rate of speed. You want to use this speed to set up a current in your pond for your koi to swim against. For the above-ground filters, with the pump before the filter, the water flow rate is slower. You don’t want to slow it down any more. Even at these slower flow rates, you do not want to create a back flow that will push against the flow of water going through the filter.

Adding lighting


The vast majority of koi ponds do not have underwater lighting. The owners feel that artificial lighting intrudes on the koi, who cannot escape the light. And the fewer electrical components that can go wrong in a pond, the better.

But if you like watching your koi swim at night, add-on lights are self-contained lights that are easily installed in any pond.

Skimmer units, protein and otherwise


The skimmer is a small surface-mounted filter system that slurps in and filters water at the pond’s surface. Skimmers are useful for removing newly fallen leaves, and they’re especially helpful if a tree overhangs your pond. Specialized skimmers that remove dissolved organic compounds along with pond surface debris are called protein skimmers or foam fractionators.
Technical Stuff
Protein skimmers are useful in koi ponds because koi are big fish that cheerfully and freely produce copious quantities of fish slime, milt, and other organic compounds. Some of this debris is dissolved in the water in the pond. Like the IRS, you can’t see it but you know it’s always there. These floating dissolved organic compounds (DOCs) are positively charged at one end and negatively charged at the other. They appear on the pond’s surface as a thin patch of scum or as persistent water bubbles. The protein skimmer hooks onto these compounds by pulling water at the pond’s surface across a bubble veil. The scum and bubbles coalesce and are swept into the collection basket, along with other floating debris.
Place your skimmer where a prevailing wind can help push surface detritus into the unit. If the skimmer is going to be plumbed into the pump, dig a trench leading to the pump using PVC piping to attach the two. Note: Skimmers may be powered by their own pump, or they may be plumbed into the main water pump. (For the latter, install a dual valve manifold in the pump intake.)
Tip
Turn off your skimmer when you feed your koi — or the skimmer may end up with the majority of the pellets.

Finishing work


The hard part about finishing work is that you’re so near yet so far. These details are critical to the success of your pond, so keep on pluggin’ away.

Heating


If you decide to heat your pond during the winter, the heater will be
- Plumbed to the water line exiting the pump for gravity-fed filters
- Plumbed to the water line exiting the filter for above-ground filters.
A pond heater uses propane or electricity to heat a small boiler, just like your own hot water heater. Water passes through the boiler, is heated, and goes back into your pond.

But before we get into a discussion about the finer points of heating your pond, how do you know if you need a heater? Ponds in areas where the nighttime temperatures routinely dip below 60 degrees F need a heater. Pond temps that go below the mid 60s are an open invitation for an Aeromonas outbreak. Aeromonas is, as you see in Chapter Diffusing Koi Stress, called “hole-in-side disease.”
How much it costs to heat your pond depends on several factors:
- Your pond size. A large pond works to your advantage when you heat it up; the larger the body of water, the more heat it retains.
- Your pond shape. A deeper pond holds heat better than a shallow pond.
- Your pond construction. A concrete-block pond holds heat better than a liner pond.
- Your pond orientation and exposure to the sun. Sun heats things up, and even winter’s weaker sun is a lot warmer than shade at that time of year. A pond in full sun stays warmer than a shaded or partially shaded pond, but you need to balance this with the more intense sun of summertime.
- Your pond covering (or lack thereof). A covered pond holds more heat than a pond with its surface area exposed to freezing air. You wouldn’t heat a garage and then leave the garage door open, would you? If you need a pond heater, cover your pond.
To apply the coating, follow these steps:
1. Mix the coating components and apply it with a roller.
You can use a paintbrush for smaller areas or places too convoluted for a roller. Texture-wise, it’s like painting with thick cream or with one of the thick latex paints designed for basement walls.
2. After the coating is dry, in two or three days, fill your pond.
No need to rinse your pond because the coating is inert, which means there’s nothing toxic to seep into the water and from there into your fish’s bodies.
Be sure you read the last section “New Pond Syndrome and What to Do about It” before you let your koi take the plunge.
Coatings come in several colors and as a clear coating. Most koi-keepers use a black coating, which shows off the colors of their koi better. The dark green is also pretty, we think.

Applying fiberglass


An alternate sealant or coating for concrete is fiberglass. This section covers the basics, but if you haven’t worked with fiberglass, we suggest you ask a pro because you’re working with finely spun glass in a resin base. For example:
- The resin cures fairly rapidly, so you don’t have much time to work with a mixed batch.
- The fiberglass cloth can shed minute fibers, which are very irritating to the skin.
- If you don’t mix the components correctly, the styrenes can leach out into the pond.
To estimate the amount you need, start with the square footage of the area to be covered — all four walls and the floor of the pond — and add 1⁄3 more for overlap and irregularities in the surface. One gallon of resin soaks 15 to 20 square feet of mat, the fiberglass “fabric.” (It’s a bit like using sheets of newspaper and flour paste but a lot more permanent.) A standard small pond, 4 feet deep and 9 x 6 feet, has 174 square feet of surface area. It will need 230 square feet of mat and 15 to 18 gallons of resin.

To apply fiberglass, follow this procedure:
1. Apply resin with a long-napped roller or a wide paintbrush to a section of the wall or floor of the pond (you’ll be doing this in sections).
2. Soak a piece of fiberglass fabric or mat with resin by dousing it in the paint tray with the resin. Apply the wetted mat to the wetted wall or floor. Smooth it into place and add resin to cover.
3. Soak another mat and place it on the resin-painted wall or pond floor, next to the first. Overlap the edges 1 to 2 inches. Rewet with resin and smooth.
4. Continue this process until you’ve covered the entire pond surface, up to the lower edge of the capstone.
5. Sand the nonconcrete components (like the drains and water returns) with a fine-grit sandpaper to create a surface the fiberglass can cling to.
6. Soak mat strips in resin and wind them around all projections for a watertight seal.
7. After you’ve applied fiberglass to the entire pond, apply a final gel-coat of fiberglass to smooth the entire surface. 
Plan to complete the application of fiberglass in one day so you create a one-piece shell on the inside of the pond. This shell needs to cure for at least a week (up to three weeks in cool weather!) before you wash and rinse the pond. Then the pond is ready for water. Fiberglass comes in clear, green, and black. As a koi keeper, you’ll probably want to opt for the black.

New Pond Syndrome and What to Do about It


Before you place your koi into your new pond, you have to make sure the pond is koi-friendly. Although you’ve followed every suggestion in building your pond, it’s not going to be a great place to put your koi — at least, not at first. We offer some suggestions on how you and your koi can get through the adjustment period.

Aging the pond water and the biological filter


Few emotions are happier than building a new pond, having all the equipment installed and working, and, with everything in place, welcoming your koi to their new home.

While your first koi or two swim around, feeding, inspecting the pond, and adding their own personal seal of approval to the waters, your biofilter begins to develop its own population of nitrifying bacteria. Strains of “Oh, happy day . . .” begin to float through the air.

Everything looks perfect, but you can tell something’s not right. The water values are just terrible. Although the koi are trying, there are no friendly bacteria in the biofilter, so the filter isn’t working as it should. The ammonia level’s too high, the nitrite level’s too high, and the pH acts like it’s on the end of a yo-yo. What’s going on?

Any new pond (and its owner) is going to suffer new-pond syndrome as the pond becomes a living organism of its own. The sky-high numbers for ammonia and nitrite and the swinging pH values are absolutely normal, and they usually last about six weeks. But as you already know, absolutely normal doesn’t mean good. That’s why you only put a couple of very ordinary koi into a new pond. These are often called canary koi, and they are used as bellwethers. They tell you if things are going as planned with the water chemistry. You hope they survive the process.

What on earth is zeolite, and why do you want it?


Zeolite is an inorganic volcanic-rock derivative that absorbs ammonia. It comes in bags, and some koi keepers replace part of the biofilter media with a mesh bag of zeolite. However, we suggest placing the bag in your filter outflow, or even in your pond, so whatever bacteria you have in your filter can multiply and be fruitful.

Every morning, you haul out the old bag of zeolite and put in a new one, but stop! You can reuse the bags. All you do is renew the zeolite by soaking the bag in a bucket of saltwater overnight. Then, simply rinse and reuse the zeolite bag.

Buy two 20-pound bags of zeolite so you can alternate their use. Soak the used bag in saltwater overnight. Then rinse it the next morning and switch it out for the other bag.

Obviously, you don’t want to do this every day for the rest of your life, but it’s doable for a week or two as your new pond becomes established. Continue to test your water values daily so you ‘ll know what’s going on. After a week, you can check the values twice a week until they drift into the normal range.
Tip
You can speed up the pond-maturation process, increase your koi’s comfort, and decrease your sleepless nights by trying one or all of the following suggestions:
- Partial water changes help (up to 10 percent of the pond’s volume a day).
- Give the filter maturation a boost by adding nitrifying bacteria to the pond (you buy these in little bottles at an aquarium store, or in larger bottles from a pond-supply store or an online pond-supply vendor).
Some of the bacteria will cling to your pond walls, but most will end up in the filter, which is where you want them.
- Add AmQuel Plus to bind up the ammonia and nitrites or add a temporary chemical filter by using Zeolite.
by R.D.Bartlett and Patricia Bartlett

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