Koi Pond Ideas: 8 Designs, Before and After

Eight koi pond ideas, each shown as a before and after picture: a natural pond with a waterfall, a formal patio pond, a Japanese pond with a bridge, a raised stone pond, a small corner pond, a pond at a deck edge, a modern concrete pond and a hillside waterfall. Below them: depth, how many koi fit, filters, liners, herons and winter.

Try a koi pond on my photo See the 8 koi pond ideas ↓

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8 koi pond ideas, before and after

In each pair, the left image was generated by AI as a stand-in for an ordinary yard, and the right image is that same picture edited by AI from a written instruction. These are not photos of real customer homes. We made them with our own AI model, which is not one of the models you can pick in the landscape tool, so a render in the tool may look different. We made each pair once and kept it, except the raised pond, which we ran a second time because the first run was not raised; each caption says what the edit did not follow, and every one of them draws far more koi than a pond that size can hold. The exact instructions are further down the page.

AI-generated example: a flat open backyard lawn with a wooden privacy fence and a row of shrubs behind, seen from the edge of a patio — Natural pond. Already in the before: the lawn, the fence, the shrubs and the patio edge. What followed the instruction: a pond in the lawn edged with rounded grey stones, a small rock waterfall at the back, water lilies and orange, white and red-and-white koi. What it did not follow: we asked for an irregular kidney shape and got a neat oval ring of similar stones, and it drew about twenty koi in a pond roughly 12 feet long, far more than the stocking rules below allow.

AI-edited version of the same image: an oval koi pond in the lawn edged with rounded grey stones, with a small rock waterfall at the back, water lilies and orange and white koi — Natural pond. Already in the before: the lawn, the fence, the shrubs and the patio edge. What followed the instruction: a pond in the lawn edged with rounded grey stones, a small rock waterfall at the back, water lilies and orange, white and red-and-white koi. What it did not follow: we asked for an irregular kidney shape and got a neat oval ring of similar stones, and it drew about twenty koi in a pond roughly 12 feet long, far more than the stocking rules below allow.

AI-generated example: a paved grey stone patio behind a modern grey stucco house with large glass doors and a lawn beyond — Formal patio pond. Already in the before: the house, the glass doors, the paving and the lawn. What followed the instruction: a rectangular pond set into the patio, a dark stone edge and thin spouts falling from a low wall at the far end. What it did not follow: we asked for three spouts and it drew two, and the edge sits up as a raised rim rather than flush with the paving. Again it is packed with koi.

AI-edited version of the same image: a rectangular koi pond set into the patio with a dark stone rim and two thin spouts of water falling from a low wall at the far end — Formal patio pond. Already in the before: the house, the glass doors, the paving and the lawn. What followed the instruction: a rectangular pond set into the patio, a dark stone edge and thin spouts falling from a low wall at the far end. What it did not follow: we asked for three spouts and it drew two, and the edge sits up as a raised rim rather than flush with the paving. Again it is packed with koi.

AI-generated example: a quiet backyard lawn with two red-leaved Japanese maples in front of a dark wooden fence, on an overcast day — Japanese pond. Already in the before: the two Japanese maples, the dark fence and the lawn. What followed the instruction: a stone-edged pond, a small arched red bridge and a stone lantern on the bank. What it did not follow: the bridge sits at the back edge of the pond rather than across its narrow middle, the stepping stones we asked for blend into the edging, and it drew around thirty koi.

AI-edited version of the same image: a koi pond edged with grey stones across the lawn, a small arched red wooden bridge at the back, a stone lantern on the bank and many koi — Japanese pond. Already in the before: the two Japanese maples, the dark fence and the lawn. What followed the instruction: a stone-edged pond, a small arched red bridge and a stone lantern on the bank. What it did not follow: the bridge sits at the back edge of the pond rather than across its narrow middle, the stepping stones we asked for blend into the edging, and it drew around thirty koi.

AI-generated example: a concrete patio beside a red brick house wall with two windows and a lawn to the left — Raised pond. Already in the before: the brick wall, the windows, the patio and the lawn. What followed the instruction: a pond built on top of the patio against the house, inside knee-high walls of stacked stone with a flat cap wide enough to sit on. What it did not follow: the spout is a thin trickle from a small grey box on the wall that looks more like an outdoor outlet than a spout, and it is packed with about twenty koi. Our first run of this instruction came out sunk almost flush with the patio, so we ran it a second time. Water weighs about 8.3 pounds a gallon, so Texas A&M AgriLife says to check structural support for any above-ground pool, and SRAC says ponds built fully above ground may have to be drained for winter.

AI-edited version of the same image: a raised koi pond standing on the patio against the brick wall, with knee-high stacked stone walls, a flat stone cap, a thin trickle of water falling in and many koi — Raised pond. Already in the before: the brick wall, the windows, the patio and the lawn. What followed the instruction: a pond built on top of the patio against the house, inside knee-high walls of stacked stone with a flat cap wide enough to sit on. What it did not follow: the spout is a thin trickle from a small grey box on the wall that looks more like an outdoor outlet than a spout, and it is packed with about twenty koi. Our first run of this instruction came out sunk almost flush with the patio, so we ran it a second time. Water weighs about 8.3 pounds a gallon, so Texas A&M AgriLife says to check structural support for any above-ground pool, and SRAC says ponds built fully above ground may have to be drained for winter.

AI-generated example: a small fenced townhouse backyard with a gravel corner, wooden fences on two sides and a potted plant — Small corner pond. Already in the before: the fences, the gravel and the potted plant. What followed the instruction: a small round pond edged with flat grey stones, with ferns and grasses tucked at the edge. What it did not follow: the bubbling rock became a small spill stone at the back, and it drew about fifteen koi in a pond about 6 feet across. By Texas A&M AgriLife's rule, a pond that size holds one or two adult koi even with a filter (see the table below).

AI-edited version of the same image: a small round pond in the gravel corner edged with flat grey stones, with ferns and grasses at the edge, a small spill stone and many koi — Small corner pond. Already in the before: the fences, the gravel and the potted plant. What followed the instruction: a small round pond edged with flat grey stones, with ferns and grasses tucked at the edge. What it did not follow: the bubbling rock became a small spill stone at the back, and it drew about fifteen koi in a pond about 6 feet across. By Texas A&M AgriLife's rule, a pond that size holds one or two adult koi even with a filter (see the table below).

AI-generated example: the back of a grey house with a low wooden deck and railing, and a flat lawn in front of the deck — Deck-edge pond. Already in the before: the house, the deck, the railing and the lawn. What followed the instruction: a pond along the front of the deck with the boards just over the water, rock edging on the lawn side and water lilies. What it did not follow: it followed this one closely; the water is greener and less clear than in the other examples. Texas A&M AgriLife and SRAC both suggest borders or decks that overhang the water by 1 to 2 inches to hide the liner edge.

AI-edited version of the same image: a koi pond along the front of the deck with the deck boards just over the water, rock edging on the lawn side, water lilies and koi — Deck-edge pond. Already in the before: the house, the deck, the railing and the lawn. What followed the instruction: a pond along the front of the deck with the boards just over the water, rock edging on the lawn side and water lilies. What it did not follow: it followed this one closely; the water is greener and less clear than in the other examples. Texas A&M AgriLife and SRAC both suggest borders or decks that overhang the water by 1 to 2 inches to hide the liner edge.

AI-generated example: a minimalist backyard with a white rendered garden wall, a row of tall slim grasses along it and a flat lawn — Modern pond. Already in the before: the white wall, the tall grasses and the lawn. What followed the instruction: a long narrow pond with smooth grey concrete edges and square concrete pads. What it did not follow: the pads are uneven in size and two of them sit on the edge instead of crossing the water, and the pond looks shallow. Koi need at least three feet of water in at least part of the pond (UF/IFAS).

AI-edited version of the same image: a long narrow koi pond with grey concrete edges in front of the white wall, with square concrete stepping pads and orange and white koi — Modern pond. Already in the before: the white wall, the tall grasses and the lawn. What followed the instruction: a long narrow pond with smooth grey concrete edges and square concrete pads. What it did not follow: the pads are uneven in size and two of them sit on the edge instead of crossing the water, and the pond looks shallow. Koi need at least three feet of water in at least part of the pond (UF/IFAS).

AI-generated example: a backyard with a grassy slope rising toward a wooden fence and evergreen shrubs along the slope — Waterfall pond. Already in the before: the fence, the evergreen shrubs and the grassy slope. What followed the instruction: a two-step rock waterfall down the slope into a pond edged with boulders and river rock, with low plants between the rocks. What it did not follow: we asked for a stream with a waterfall and got a short cascade with no stream, and the pond again holds far too many koi. SRAC says waterfalls and fountains help keep oxygen up.

AI-edited version of the same image: a two-step rock waterfall running down the slope into a koi pond edged with boulders and river rock, with low plants between the rocks and many koi — Waterfall pond. Already in the before: the fence, the evergreen shrubs and the grassy slope. What followed the instruction: a two-step rock waterfall down the slope into a pond edged with boulders and river rock, with low plants between the rocks. What it did not follow: we asked for a stream with a waterfall and got a short cascade with no stream, and the pond again holds far too many koi. SRAC says waterfalls and fountains help keep oxygen up.

How deep a koi pond should be

Koi need a deep section, both to get through winter and to stay cool in summer. SRAC says large koi tend to lose color and become stressed without a cool place to stay in hot weather. The sources do not agree on one number:

Depth advice for koi and fish ponds, by source.
Source	Depth
UF/IFAS Extension	At least 3 ft for koi; some koi experts say 6 ft
SRAC 435 (1999)	A section 3 to 4 ft deep that does not freeze; 18 to 24 in is enough in the deep south with only a few fish and plenty of plant shade
Texas A&M AgriLife (2014)	Most ponds 18 to 24 in, with sections 3 to 5 ft deep
Washington Koi & Water Garden Society	Some water at least 4 ft deep (Puget Sound)
Penn State Extension	At least 2 ft for most fish, depending on the fish

So plan on at least 3 feet in the deepest part, more where winters are long. The deep part does not have to be the whole pond: SRAC suggests cutting the sides into 2 or 3 tiers about 12 inches wide, which help hold the liner in place and give ledges for plants, and both SRAC and Texas A&M AgriLife suggest a catch basin 6 to 12 inches deeper than the bottom to gather fish and debris when you drain it.

How many koi a pond can hold

Every one of our AI pictures shows far too many fish. Texas A&M AgriLife's basic rule is no more than 1 pound of adult fish per 100 gallons, or 2 pounds with a bio-filter and strong aeration, and it says adult koi of 4 to 5 pounds are common in small ponds. Here is what that rule gives for four pond sizes:

Adult koi at 4 to 5 lb each, by Texas A&M AgriLife's 1 lb and 2 lb per 100 gallon rules. Gallons = length × width × average depth × 7.48 (for a round pond, 3.14 × radius² × average depth × 7.48).
Pond	Gallons	No filter	Filter + aeration
6 ft round, 2 ft avg deep	about 420	0–1	1–2
8 × 5 ft, 2.5 ft avg	about 750	1	2–3
10 × 6 ft, 3 ft avg	about 1,350	2–3	5–6
15 × 9 ft, 3 ft avg	about 3,030	6–7	12–15

Other sources land on either side of that. SRAC's surface-area rule is more generous: one 12-inch fish per 4.5 square feet without aeration, which it works out to 20 adult koi for a 9 by 15 foot pond. The Washington Koi & Water Garden Society says koi in a small, well-filtered pond need at least a couple hundred gallons each and even then may not grow well, and that many koi keepers keep 1,000 gallons per fish, which would mean 3 koi in the largest pond above. SRAC also notes that top exhibitors in Japan stock only 10 to 15 koi even in large ponds. UF/IFAS says a fish pond should be at least 500 gallons. Koi grow: Texas A&M AgriLife says they can live 60 to 70 years, though 20 or less is more common in ponds, so stock for their adult size, not the size at the store.

Filters, pumps and oxygen

Do you need a filter?: SRAC says water gardens with lots of plants and a modest number of fish should not need one. Penn State says you will need one if you plan to keep a large number of fish, which a koi pond usually means.
Two kinds of filter: Mechanical filters (leaf skimmers, foam filters, settling basins) trap dirt and debris; biological filters use bacteria to break down fish waste (SRAC, Texas A&M AgriLife). Bio-filters work best at a pH of 7 to 8 and an alkalinity above 50 ppm.
Plant filter: Texas A&M AgriLife describes a plant basin about 10 percent of the pond's surface area, with the pond water run through it every 2 to 4 hours.
Pump: Pumps are sized by the gallons per hour they move; put the pump at the bottom but raised slightly so it does not clog (Penn State). Plan where pipes, filters, lights and heaters will be hidden before you dig (Texas A&M AgriLife).
Oxygen: Fish become severely stressed below 3 ppm of dissolved oxygen and die at about 1 ppm (SRAC). Waterfalls, fountains and air diffusers help keep it up. Fish gulping at the surface is a sign of low oxygen, and Texas A&M AgriLife says more aeration is the best fix.

None of the extension sources we read gives a pump turnover rate, bottom drain or skimmer sizing for a koi pond, so we do not give one here; ask a pond supplier to size the pump and filter to your pond's gallons.

Pond liners: EPDM, PVC, preformed or concrete

EPDM rubber: The most common liner in ornamental ponds, because it is flexible and resists punctures and UV light (Texas A&M AgriLife); Penn State calls it the most popular with pond builders.
PVC or polyethylene: Usually the least expensive (Penn State).
Preformed plastic or fiberglass: Lasts the longest (Penn State), but SRAC says preformed ponds are shallow and not the best habitat for large fish.
Concrete: Very long life and can be tiled, but expensive, can crack and leak, and must be cured (SRAC); Penn State calls it difficult to work with.
How long liners last: SRAC (1999) says flexible liners usually last 10 to 20 years; Penn State (2024) says most newer liners are guaranteed for 25 to 50 years or longer.
Sizing and fitting: Measure the longest length and width including the depth, and add about 2 feet to each (Penn State). Texas A&M AgriLife allows 1 to 3 feet on each side for burying the edge, and says to pack the hole with sand first so roots and rocks do not puncture the liner.

Where to put a koi pond

Sun and shade: At least 6 hours of sun a day (SRAC, UF/IFAS), but SRAC warns that direct midday sun in the warmest months can overheat a shallow pond, and Penn State says some shade is ideal, especially for a small pond.
Not under trees: Roots get in the way of digging and may cause damage later (SRAC).
Away from runoff: Keep lawn and road runoff out (Penn State). Texas A&M AgriLife says to site the pond slightly higher than the ground around it, where the water table stays below the bottom; Penn State says a high water table will make the liner buckle.
In view of the house: Easier to enjoy, to watch children and pets, and to spot predators, and cheaper to run pipes and power to (Texas A&M AgriLife).
Power and buried lines: A pump needs an approved outdoor outlet, which may need an electrician (Penn State). Call the utility companies before digging (SRAC).

Keeping herons and raccoons away from koi

Bright koi are easy to spot. Virginia Cooperative Extension says koi and goldfish are extremely vulnerable to predators and need places to hide, and the Washington Koi & Water Garden Society lists herons, raccoons, kingfishers and cats among them.

Depth: At least 3 feet gives fish a safe retreat from birds and from raccoons (Texas A&M AgriLife). UF/IFAS adds that a deep pond stops wading birds from standing in it to hunt.
Hiding places: Make the middle deeper and add overhanging rock ledges (UF/IFAS).
Netting: A net over the pond reduces bird predation (SRAC). Virginia Cooperative Extension warns that birds can get tangled, so keep it taut.
Steeper edges: Virginia Cooperative Extension suggests a steeper shoreline against herons and egrets.
Raccoons: Virginia Cooperative Extension says fencing and repellents do not work on raccoons; it suggests netting over the pond.

Koi in winter and summer, and how to feed them

Winter: The deep section that does not freeze is where koi spend the winter (SRAC). The Washington Koi & Water Garden Society says koi can live in water down to 38°F, and slow down and eat very little until spring. Keep part of the surface open with a surface aerator so gases can escape (Illinois Extension); Penn State mentions a pond heater as another option.
Summer: The same deep water is the cool retreat koi need in hot weather (SRAC). Texas A&M AgriLife says to feed early in the morning in hot months, since warm water and heavy feeding can lead to low oxygen.
How much to feed: About 1 percent of the fishes' weight a day keeps adult fish healthy; 3 percent a day in water above 70°F is for fast growth (SRAC, Texas A&M AgriLife). Fish should finish the food in about 5 minutes; remove anything left after 15.
When to stop: SRAC says fish do not feed in water below 45°F, and to feed less when the water is above 90°F.

Plants in a koi pond

Floating plants and lilies shade the water and hold back algae. SRAC suggests covering 50 to 75 percent of the surface; UF/IFAS says no more than two-thirds, and Penn State no more than 70 percent. Koi root around in pots: SRAC and Texas A&M AgriLife suggest wire or plastic net enclosures to protect plants, while the Washington Koi & Water Garden Society says koi are usually hunting bugs in the plants rather than eating them. Either way, pot the plants and expect some damage. Never release koi or pond plants into the wild: SRAC lists koi and many pond plants as non-native species that should never be allowed to escape.

Safety and permits

SRAC and Texas A&M AgriLife both say insurance companies may treat a pond deeper than 18 inches as an "attractive nuisance", and SRAC says it may need to be fenced. Penn State says even a small pond can be dangerous for small children and to check local rules on water depth and fencing before you dig.

How to try a koi pond on a photo of your yard

Take a photo of the spot from where you would normally see the pond, in daylight, with the whole area in frame.
Open the landscape tool, choose Custom, and paste one of the instructions below into the Custom Design Requirements box.
Change the pond shape, the edging and what must stay, then generate.
If it misses something, as every one of our examples did in some detail, reword that part and run it again.

The picture shows the look and where the pond would sit. It does not measure depth or volume, and it does not know how many fish fit, so plan those with the tables above.

Koi pond instructions to paste into Custom mode

These are the exact instructions we used for the 8 examples above, in the same order. In the landscape tool, choose Custom, paste one into the Custom Design Requirements box, then upload a photo of your yard or patio. Swap in your own pond shape, edging and what must stay.

Add ONLY a natural-looking koi pond in the middle of the lawn: an irregular kidney shape about 12 feet long edged with rounded grey boulders and river rock, a small rock waterfall at the back end, water lilies on one side, with several orange, white and red-and-white koi fish clearly visible swimming in clear water. Keep the house, the fence, the trees and the camera angle exactly the same.
Add ONLY a formal rectangular koi pond set into the patio, about 10 feet by 5 feet, with a smooth dark stone coping edge flush with the paving and three thin sheet-water spouts falling from a low wall at the far end, with several orange, white and red-and-white koi fish clearly visible swimming in clear water. Keep the house, the glass doors, the paving around it and the camera angle exactly the same.
Add ONLY a Japanese-style koi pond across the lawn: an irregular pond edged with grey stones and moss, a small arched red wooden bridge over the narrow middle, a stone lantern on the bank and a few stepping stones leading to it, with several orange, white and red-and-white koi fish clearly visible swimming in clear water. Keep the maples, the fence and the camera angle exactly the same.
Add ONLY a raised koi pond built on top of the patio against the house wall. The pond is NOT dug into the ground: it sits entirely above the patio paving, inside a rectangular box of stacked natural stone walls about 8 feet long that rise knee-high, about 2 feet above the patio, so the outer stone faces of the walls are clearly visible standing up from the paving, with a flat stone cap on top you could sit on. A small spout of water falls into it from the house wall. Several orange, white and red-and-white koi swim in clear water inside the raised walls. Keep the brick wall, the windows, the lawn and the camera angle exactly the same.
Change ONLY the gravel corner: make it a small round koi pond about 6 feet across edged with flat grey stones, a short bubbling rock in it, ferns and grasses tucked at the edge, with several orange, white and red-and-white koi fish clearly visible swimming in clear water. Keep the fences, the potted plant and the camera angle exactly the same.
Add ONLY a koi pond along the front edge of the deck so the deck boards overhang the water by a few inches, the pond curving out into the lawn with rock edging on the lawn side and a few water lilies, with several orange, white and red-and-white koi fish clearly visible swimming in clear water. Keep the deck, the house, the railing and the camera angle exactly the same.
Add ONLY a modern koi pond in front of the white wall: a long narrow rectangle with smooth grey concrete edges, three square concrete stepping pads crossing the water, with several orange, white and red-and-white koi fish clearly visible swimming in clear water. Keep the white wall, the grasses, the lawn and the camera angle exactly the same.
Add ONLY a koi pond at the bottom of the slope with a stream and a two-step rock waterfall coming down the slope into it, boulders and river rock along the edges, low plants between the rocks, with several orange, white and red-and-white koi fish clearly visible swimming in clear water. Keep the fence, the evergreen shrubs and the camera angle exactly the same.

Try a koi pond on my photo

Koi pond questions

How deep should a koi pond be?

At least 3 feet in the deepest part (UF/IFAS), and some koi experts say 6 feet. SRAC suggests a section 3 to 4 feet deep that does not freeze, and Texas A&M AgriLife sections 3 to 5 feet deep. The rest of the pond can be shallower, on tiers.

How many koi can I put in my pond?

Texas A&M AgriLife's rule is 1 pound of adult fish per 100 gallons, or 2 pounds with a bio-filter and strong aeration. With adult koi at 4 to 5 pounds, a 400 gallon pond holds about 2 adult koi with a filter. Many koi keepers allow 1,000 gallons per fish (Washington Koi & Water Garden Society).

How do I work out how many gallons my pond holds?

Length × width × average depth in feet × 7.48. For a round pond, 3.14 × radius² × average depth × 7.48. A 10 by 6 foot pond with an average depth of 3 feet holds about 1,350 gallons.

Does a koi pond need a filter?

Usually. SRAC says ponds with lots of plants and only a modest number of fish may not, but Penn State says you need one if you keep many fish. Most koi ponds use a mechanical filter for debris and a biological filter for fish waste.

What is the best liner for a koi pond?

EPDM rubber is the most popular with pond builders (Penn State). PVC is cheaper. Preformed ponds last long but are shallow and not the best for large fish (SRAC). Concrete lasts longest but costs more and can crack.

How do I keep herons away from my koi?

Make the pond at least 3 feet deep so birds cannot stand in it (UF/IFAS, Texas A&M AgriLife), add overhanging rock ledges to hide under, and put a taut net over the pond (SRAC, Virginia Cooperative Extension).

Do koi need to be fed in winter?

No. SRAC says fish do not feed in water below 45°F. Koi slow down in cold water and eat very little until spring. Keep part of the surface open with an aerator so gases can escape.

Can I see a koi pond on a photo of my own yard?

Yes. Upload a photo to the landscape tool, choose Custom, and describe the pond: its shape, edging, waterfall and what must stay. The result is a picture for planning, not a measured plan.

Is the koi pond tool free?

You need an account, and it is free: 1 free render with a free account (sign in with Google or an email code). More renders come with a paid plan.

Sources for the koi pond facts

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