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How to Calculate Pond Volume

There are 7.5 gallons of water for every cubic foot of liquid volume in your pond. With this in mind, the way to calculate the number of gallons in your pond is to first calculate the pond volume and multiply by 7.5. Calculate the volume as follows:

For a pond 20 ft. long, 15 ft. wide with an average depth of 2 ft., the volume can be calculated as: 20 ft. x 15 ft. x 2 ft. = 600 cubic ft. x 7.5 gal./cu. ft. = 4,500 gallons If you find it hard to believe that you have that much water in your pond, that is a typical reaction! What is even more surprising to most people is that this is almost 20 tons of water—a good reason to have a certified pond installer install your pond, or a knowledgeable pond specialist from your local pond supply store help you out.

CIRCULAR POND : Multiply the RADIUS (one half of the diameter) x the RADIUS x 3.14 x the DEPTH (avg.)
For a pond that is 30 ft. in diameter with an average depth of 3 ft. , calculate the volume as: 15 ft. x 15 ft. x 3.14 x 3 = 2, 120 cu. ft. x 7.5 gal./cu. ft. = 15, 900 gal.

LARGE POND OR LAKE IN ACRES : If you know the surface area, the gallons can be calculated by Multiplying the AREA in ACRES by 326,700 gallons for every ft. of pond depth.
Example: For a pond or lake that is 2.5 acres with an average depth of 7 ft., calculate the volume as: 2.5 acres x 7 ft. x 326,700 gal./acre-ft. = 5,717,250 gallons.

IRREGULARLY SHAPED PONDS: It is best to break down the pond into sections and calculate the volume of each section individually, then total them.

Monitoring Your Pond

While most people who own a swimming pool regularly monitor the water quality of their pool, far fewer pond owners do the same even though it is equally or more important, especially if you have fish.

We recommend that the following parameters be monitored weekly: pH, ammonia nitrogen, nitrate nitrogen, phosphate, and alkalinity. Other parameters that can be useful to monitor are: dissolved oxygen, hardness, iron, and copper. Test kits are readily available at your local water gardening specialty center that will allow you to do the majority of these tests.

Many people see the need to monitor these parameters only when having problems, but it is also important to have a baseline when everything is fine so that you can analyze what is changing when you do experience problems.

The Natural Cycles

While many pond owners may view using bacteria as an unusual way to purify their water, it is actually the most natural way to do it! That is how nature cleans the environment. Ultimately all waste products in the environment have to be recycled back to the biosphere and bacteria are nature’s recyclers.

The most important of these cycles from the standpoint of a pond is the Nitrogen Cycle. One of the common byproducts of protein breakdown, like the protein in fish food, is ammonia.

This ammonia can be toxic to fish and other aquatic life in concentrations as low as 1.0 mg/L depending on the pH. The fish emits this through their gills. The majority of the ammonia in the pond can be traced to this source. Some can also be traced to the breakdown of uneaten fish food and plant material.

When a pond is conditioned or capable of cycling, it means that the necessary bacteria have been developed to convert the ammonia to nitrite and, subsequently, nitrate. In many ponds this nitrate can accumulate and provide nutrients for unwanted plant growth.

MICROBELIFT/ PL allows your pond to take the nitrogen cycle another step by further chemically reducing the nitrate to nitrogen gas, which harmlessly bubbles out of the pond. Another of the important natural cycles is the carbon cycle. All living things comprise primarily carbon. Fish waste contains a carbonaceous component. Much of the sludge that builds up on the bottom of most ponds is organic, which means it is made up of carbon compounds. Other bacteria in MICROBE-LIFT/PL known as heterotrophs break down this sludge and convert it to carbon dioxide and water.

Used in conjunction with MICROBELIFT/ SLUDGE AWAY, MICROBE-LIFT/PL can keep most ponds clean and sludge free.


It is best for most ponds to have a pH in the range of 7.6 to 8.2 While many ponds do operate outside of this range, it isn’t the best condition for the aquatic life. In certain areas of the country the pH can be naturally lower or higher, depending on certain environmental conditions. If the pH is too low, it may be difficult to establish nitrification. When adjusting pH, it should be done gradually.

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