How can I figure how many fish I need to run a balanced system, if the planting bed is 16 feet long, 4 feet wide what will be the fish tank size and how many fish will be needed to supply the needed nitrates for the plants?
This was a question posted to me and I think that it makes for a good topic. Here is the way to go about solving this problem.
Looking at the dimensions, 16′ x 4′ ( I’m guessing about 6″-8″ deep of grow medium) we solve to find the area of your grow bed. So, we take 16′ x 4′ = 64 Sq Ft x (6″). 6″ is really 6 divided by 12 to get .5 or 1/2 of one foot. So, 64 x .5 is 32 Cubic Ft. If you have 8″ of grow media you would multiply 64 x (8″ divided by 12″ = .67) = 42.67 cubic ft.
The rule of thumb is for every cubic ft of water you need 2 cubic ft of grow media. With that in mind we take 32 cubic ft. divided by 2 to get 16 cubic ft of water and for the other measurement 42.67 we would need 21.34 cubic ft of water.
There are 7.5 gallons of water in a cubic ft. So, 7.5 x 16 = 120 gallons. (for the other measurement 21.34 x 7.5 = 160 gallons)
Therefore you would need a 120 to 160 gallon fish tank to support this size grow bed.
The other rule of thumb is ruffly 1″ of fish per gallon of water. Example, might be having a 120 fish, 1″ in length or 60 fish 2″ in length. You get the idea.
I hope that has helped. If you have any other questions please feel free to e-mail any time.
Thanks and have a wonderful day.
John
