When designing a pond, you think about shape, location, plant shelves, and depth. You want the pond to be deep enough to allow your fish to survive freezing in the winter and overheating in the summer. This depth is usually 24 to 36 inches. Planting shelves are usually 12 to 18 inches deep. So you have your design all figured out, and your ready to dig right? Well before you do, consider this.
Planting Shelves are a convience, but they waste precious liner. Take a 20 foot by 20 foot rectangular pond that is 3 foot deep. There is a shelf for plants 18 inches deep and 24 inches wide all the way around the pond. This shelf is completely square and uses up 216 cubic feet of space. By removing this shelf, and just making the walls vertical to the bottom, you could gain about 1620 gallons. What to do with my plants you ask? Try putting them on plastic milk crates or treated cement blocks. It provides a place for fish to hide from birds and the heat of the sun. It allows you to rearrange plants at random. It provides more deep water to help maintain temperature. To overwinter your plants, simply remove the crate and lower the plant down to the bottom. By placing the plants slightly away from the edge, it will create a buffer zone to discourage animals from getting into your pond.
Now lets look at the dimensions. A 20 foot by 20 foot rectangular pond 3 foot deep is approximately 9000 gallons. With the same amount of liner, you could make it 18 foot by 18 foot and 4 foot deep and have 9720 gallons. Now 720 gallons extra might not seem like much more water, but if you are raising KOI, every little bit counts. On another note, you don't want to make the pond too deep, or you will loose gallons. If you made the pond 14 foot by 14 foot by 6 foot deep you would get 8820 gallons, thats a loss of 900 gallons.
I'm not suggesting that your pond can only be rectangular, the optimization method will work for any shape as long as the walls of the pond are vertical all the way to the bottom. If you have plant shelves or a sloping bottom the results may be unpredictable. I used the rectangular shape as a benchmark since its volume is easier to calculate.
To calculate the optimum gallons per liner, follow the steps below. Before you begin, subtract 2 feet from the length and width of the liner, this part of the liner will be used for overlap on the pond edges.
Step 1: Subtract 1 foot from the length and width, add 6 inches to the depth
Step 2: Calculate the Gallons (Gallons = Length * Width * depth * 7.5)
Step 3: Repeat Step 1 until the Gallons starts Decreasing
Example # 1
liner is 20 by 20, remove the edges and it is 18 by 18. You can see that size #5 is the optimum size for this liner and is 300 gallons (10%) larger than size #3. The bigger the liner, the deeper the pond should be.
Example #2
liner is 30 by 30, remove the edges and it is 28 by 28. You can see that size #8 is the optimum size for this liner, and is 3543 Gallons (41%) larger than size #3, and 1293 gallons (12%) larger than size #5.
Ok, so now you have the right dimensions, and your ready to dig right? Well, not so fast my friend. What if I told you that we can still add a few more gallons to the pond. Heres how, by softening the edges all around the bottom of the pond to a 45 degree angle, we can gain an additional 6 inches to the depth of the pond.
Lets calculate the gallons difference. The pond started out 6 foot wide by 14 foot long by 2 foot deep (6*14*2*7.5 = 1260 gallons). The pond is now 6 foot wide by 14 foot long by 2 feet 6 inches deep (6*14*2.5*7.5 = 1575 gallons). To calculate the volume from the edge that we removed, (length + width - 1) * 7.5 or ((14 + 6 - 1) * 7.5) = 142.5 gallons. So 1575 - 142.5 = 1432.50 gallons. Thats a gain of 172 gallons.
Lets try this with a larger pond. 20 foot wide by 20 foot long by 3 foot deep (20*20*3*7.5 = 9000 gallons). Soften the edges and it is now 20 foot wide by 20 foot long by 3 foot 6 inches deep (20*20*3.5*7.5 = 10500 gallons), subtract the edge ((20+20-1)*7.5) = 292.5 gallons. So 10500 - 292.5 = 10207.5 gallons. Thats a gain of 1207.5 gallons.
So with all things considered, here are some common Liner Sizes & Their Optimum Dimensions.
Need Some help calculating the right size, check out my Pond Volume Calculator
Planting Shelves are a convience, but they waste precious liner. Take a 20 foot by 20 foot rectangular pond that is 3 foot deep. There is a shelf for plants 18 inches deep and 24 inches wide all the way around the pond. This shelf is completely square and uses up 216 cubic feet of space. By removing this shelf, and just making the walls vertical to the bottom, you could gain about 1620 gallons. What to do with my plants you ask? Try putting them on plastic milk crates or treated cement blocks. It provides a place for fish to hide from birds and the heat of the sun. It allows you to rearrange plants at random. It provides more deep water to help maintain temperature. To overwinter your plants, simply remove the crate and lower the plant down to the bottom. By placing the plants slightly away from the edge, it will create a buffer zone to discourage animals from getting into your pond.
Now lets look at the dimensions. A 20 foot by 20 foot rectangular pond 3 foot deep is approximately 9000 gallons. With the same amount of liner, you could make it 18 foot by 18 foot and 4 foot deep and have 9720 gallons. Now 720 gallons extra might not seem like much more water, but if you are raising KOI, every little bit counts. On another note, you don't want to make the pond too deep, or you will loose gallons. If you made the pond 14 foot by 14 foot by 6 foot deep you would get 8820 gallons, thats a loss of 900 gallons.
I'm not suggesting that your pond can only be rectangular, the optimization method will work for any shape as long as the walls of the pond are vertical all the way to the bottom. If you have plant shelves or a sloping bottom the results may be unpredictable. I used the rectangular shape as a benchmark since its volume is easier to calculate.
To calculate the optimum gallons per liner, follow the steps below. Before you begin, subtract 2 feet from the length and width of the liner, this part of the liner will be used for overlap on the pond edges.
Step 1: Subtract 1 foot from the length and width, add 6 inches to the depth
Step 2: Calculate the Gallons (Gallons = Length * Width * depth * 7.5)
Step 3: Repeat Step 1 until the Gallons starts Decreasing
Example # 1
liner is 20 by 20, remove the edges and it is 18 by 18. You can see that size #5 is the optimum size for this liner and is 300 gallons (10%) larger than size #3. The bigger the liner, the deeper the pond should be.
| Size | Length | Width | Depth Feet - Inches |
Gallons |
|---|---|---|---|---|
| 1 | 16 | 16 | 1 - 0 | 1920 |
| 2 | 15 | 15 | 1 - 6 | 2530 |
| 3 | 14 | 14 | 2 - 0 | 2940 |
| 4 | 13 | 13 | 2 - 6 | 3168 |
| 5 | 12 | 12 | 3 - 0 | 3240 |
| 6 | 11 | 11 | 3 - 6 | 3176 |
Example #2
liner is 30 by 30, remove the edges and it is 28 by 28. You can see that size #8 is the optimum size for this liner, and is 3543 Gallons (41%) larger than size #3, and 1293 gallons (12%) larger than size #5.
| Size | Length | Width | Depth Feet - Inches |
Gallons |
|---|---|---|---|---|
| 1 | 26 | 26 | 1 - 0 | 5070 |
| 2 | 25 | 25 | 1 - 6 | 7031 |
| 3 | 24 | 24 | 2 - 0 | 8640 |
| 4 | 23 | 23 | 2 - 6 | 9918 |
| 5 | 22 | 22 | 3 - 0 | 10890 |
| 6 | 21 | 21 | 3 - 6 | 11576 |
| 7 | 20 | 20 | 4 - 0 | 12000 |
| 8 | 19 | 19 | 4 - 6 | 12183 |
| 9 | 18 | 18 | 5 - 0 | 12150 |
Ok, so now you have the right dimensions, and your ready to dig right? Well, not so fast my friend. What if I told you that we can still add a few more gallons to the pond. Heres how, by softening the edges all around the bottom of the pond to a 45 degree angle, we can gain an additional 6 inches to the depth of the pond.
Lets calculate the gallons difference. The pond started out 6 foot wide by 14 foot long by 2 foot deep (6*14*2*7.5 = 1260 gallons). The pond is now 6 foot wide by 14 foot long by 2 feet 6 inches deep (6*14*2.5*7.5 = 1575 gallons). To calculate the volume from the edge that we removed, (length + width - 1) * 7.5 or ((14 + 6 - 1) * 7.5) = 142.5 gallons. So 1575 - 142.5 = 1432.50 gallons. Thats a gain of 172 gallons.
Lets try this with a larger pond. 20 foot wide by 20 foot long by 3 foot deep (20*20*3*7.5 = 9000 gallons). Soften the edges and it is now 20 foot wide by 20 foot long by 3 foot 6 inches deep (20*20*3.5*7.5 = 10500 gallons), subtract the edge ((20+20-1)*7.5) = 292.5 gallons. So 10500 - 292.5 = 10207.5 gallons. Thats a gain of 1207.5 gallons.
So with all things considered, here are some common Liner Sizes & Their Optimum Dimensions.
| Liner Width x Length |
Pond Width x Length |
Pond Depth |
Optimum Gallons |
|---|---|---|---|
| 10 x 10 | 6 x 6 | 1.5 | 323 |
| 10 x 15 | 5 x 10 | 2.0 | 645 |
| 10 x 20 | 5 x 15 | 2.0 | 983 |
| 12 x 20 | 6 x 14 | 2.5 | 1433 |
| 15 x 15 | 9 x 9 | 2.5 | 1391 |
| 15 x 20 | 9 x 14 | 2.5 | 2197 |
| 15 x 25 | 8 x 18 | 3.0 | 3053 |
| 15 x 30 | 8 x 23 | 3.0 | 3915 |
| 20 x 20 | 13 x 13 | 3.0 | 3615 |
| 20 x 25 | 12 x 17 | 3.5 | 5145 |
| 20 x 30 | 11 x 21 | 4.0 | 6698 |
| 20 x 35 | 11 x 26 | 4.0 | 8310 |
| 20 x 40 | 11 x 31 | 4.0 | 9923 |
| 20 x 45 | 11 x 36 | 4.0 | 11535 |
| 20 x 50 | 11 x 41 | 4.0 | 13148 |
| 30 x 30 | 19 x 19 | 5.0 | 13260 |
| 30 x 35 | 19 x 24 | 5.0 | 16785 |
| 30 x 40 | 18 x 28 | 5.5 | 20453 |
| 30 x 45 | 18 x 33 | 5.5 | 24127 |
| 30 x 50 | 17 x 37 | 6.0 | 27908 |
| 30 x 55 | 17 x 42 | 6.0 | 31695 |
| 30 x 60 | 17 x 47 | 6.0 | 35483 |
| 40 x 40 | 26 x 26 | 6.5 | 32573 |
| 40 x 50 | 25 x 35 | 7.0 | 45495 |
| 40 x 60 | 24 x 44 | 7.5 | 58898 |
| 40 x 70 | 23 x 53 | 8.0 | 72578 |
| 40 x 80 | 22 x 62 | 8.5 | 86333 |
| 50 x 50 | 33 x 33 | 8.0 | 64853 |
| 50 x 60 | 31 x 41 | 9.0 | 85260 |
| 50 x 70 | 30 x 50 | 9.5 | 106283 |
| 50 x 80 | 29 x 59 | 10. | 127673 |
| 50 x 90 | 29 x 69 | 10. | 149348 |
| 50 x 100 | 28 x 78 | 10. | 171203 |
Need Some help calculating the right size, check out my Pond Volume Calculator