Pond Calculations

Determining Approximate Gallons of Water


You will need to know the total gallons of water your pond has to be able to determine pump size, filtration, fish capacity and correct dosages for water and fish treatments.

Multiply the average length of the pond by the average width and then by the average depth. This will give you the total cubic feet of water. There are 7.48 gallons per cubic foot so you can multiply your total cubic feet by 7.48 to get your total gallons of water in your pond.
***You can use 7.5 - that's close enough.

L X W X D X 7.5 = pond gallons

Number of Fish Recommended


There are a couple of general rules to determine how many fish your pond can sustain. Unless you have an elaborate filtration system, it's better to have fewer fish than more. Too many fish can quickly overload the pond with high amounts of ammonia that may spike in the hot summer months, causing the loss of all the fish over night.

The total surface area, size and type of filtration system, flow rate, temperature and climate should all be considered when determining the right amount of fish for your pond.

* One 6" fish for every hundred gallons of water OR

* 1" of fish per 10 gallons of water OR

* Total gallons of pond divided by 200 = Total 6" fish in pond

Determining Liner Size


Most ponds are not just one length. Actually the ideal pond should have 3 depths. The first one should be 6-10" for marginal plants, the second depth should be 12-18" for lilies, lotus and submerged plants and the third depth should be 2-3' for fish and over wintering plants. Add at least 2' for overlapping along the edge of the pond.

The length of liner = max length of pond + (2 times max depth) + minimum of 2' overlap.

The width of liner = max width of pond + (2 times max depth) + minimum of 2' overlap.