While doing some research on my spreadsheet program I came across a formula that some of you pond lovers might enjoy:

Number of Fish You Can Keep = (4G)/(A^2)  Where G is the size of the pond in gallons and A is the average adult size of fish you plan on keeping.

For instance, if you have a 1,000 gallon pond and want to keep fish that can grow about a foot long, then you should keep no more than 27 fish (4 x 1,000 / 12^2 = 4,000 / 144 = 27.7...). This guideline works pretty well for cyprinids maintained with additional food added to the system.

For other fish and systems to which you do not wish to add extra food, the following formula is better:

Number of Fish You Can Keep = (2G)/(A^2)

I know that most of you already have your own guidelines and have enough experience to predict suitable stocking levels, but I thought I'd add it for the fun of it.

"Tears aren't a sign of weakness, they're a sign of poor plumbing."

--Dead Men's Lies

I must say though that I don't think it would work out with my pond- planted or not. I just can't see 6.9 adult koi in my 500gal pond... (using 2G/12^2)

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"For this they willingly are ignorant of, that by the word of God the heavens were of old, and the earth standing out of the water and in the water: whereby the world that then was, being overflowed with water, perished" (2nd Peter 3:5-6)

Yeah, the formula gives a bioload level, but it doesn't tell you whether or not the environment size is appropriate. In other words, this is just a fun little self-check formula that doesn't trump common sense. Nonetheless, this formula (2G/A^2) is still more conservative than some of the pond guidelines out there. For instance, PetSmart suggests 50 gallons per individual koi. Using that rule, your 500 gallon pond could house 10 koi (500/50 = 10)!!!

A little better rule for checking suitable environment size is G = 0.4 x A^3. The only problem with this one is that it doesn't predict how many fish can go into the environment. That is where the other formula comes into play. despite all this, they're still just guidelines--to a mathematician they're fun, but they don't really serve a practical purpose.

"Tears aren't a sign of weakness, they're a sign of poor plumbing."

--Dead Men's Lies

"Tears aren't a sign of weakness, they're a sign of poor plumbing."

--Dead Men's Lies

"For this they willingly are ignorant of, that by the word of God the heavens were of old, and the earth standing out of the water and in the water: whereby the world that then was, being overflowed with water, perished" (2nd Peter 3:5-6)