Organic Food For All

By John Stivers

How many fish to run a balanced Aquaponic system?

Posted by offa on March 29, 2009

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. 


4 Responses to “How many fish to run a balanced Aquaponic system?”

  1. Rick Lehtinen said

    Hi, John:

    Well, this afternoon I went out and bought three tanks like the one shown in your video. One is for home potable water storage. One is for use as a rain barrel to keep my grow boxes going. The third I’d like to use to make a system like yours. (I was excited about a barrel-ponics system, but yours looks easier, and I will get experience with continuous flow).

    You go kind of quick with the skill sawing and the hack sawing. Do you have some kind of a sketch I can work from?

    I am writing from Mesa, Arizona, where it can get kind of hot. Any suggestions?



  2. kerwin said

    hi! i’m from the philippines, and i have recently started my 1st aquaponic system. i used a 35gallon aquarium, and for my grow bed, a 14″ x 30″ x 8″ multipurpose storage box. my system is a floating system. part of the grow bed, 16″ x 7″ x 8″ area, serves as the filter, where i placed some foam as filtering media. the whole box is then flooded, and i have a 1″ styro sheet which serves as my floater, and six stryro cups filled with aquarium pebbles as my grow media. for my aquarium, i placed 12 cichlids, but i plan to add more. i tried to plant parsley, okra, and philippine lemon on my system. i sowed the seeds in the pebbles, and after almost 2 weeks, the parsley started to germinate. the philippine lemon is starting to show some signs of life, but i think the okra seeds are spoiled. is there a faster way of germinating seeds? can i use plant cut outs and just stick them on my grow bed? hope you can help me on this. i will try to take some pictures of my system and send them to you. thanks in advance!

  3. Fish Tank Installation…

    […]How many fish to run a balanced Aquaponic system? « Organic Food For All[…]…

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