A Community and Forum For Aquaponic Gardeners

Trough Size?

Hi. I'm am new to aquaponics. I have been reading and studying for a couple of weeks and I can't wait to build my first system. I have a couple of questions that I feel need to be answered before I can feel confident to start buying the parts. I hope someone can help.

My question concerns the ratio (if one exists) between fish tank size and trough size. I know there are a gazillion factors resulting in a gazillion answers but lets try to keep it simple. I have searched this forum a lot for discussions about this but all I seem to find are discussions about the ratio of fish tank size to "media" grow bed size. It seems well communicated on this forum that the ratio of FT to GB is 1:1 or 1:2. But this concerns a grow bed with media. I'm looking for some type of general answer to the ratio of FT size to trough size utilizing DWC. I know this depends a lot on other factors such as fish density, water temperature, type of plants and a host of other factors, but I wonder if there could be some type of general guideline to help beginners like me; some general specification that can launch further experimentation with my own particular factors.

I will probably be using a 150 gallon fish tank and will most likely stock the fish tank with 20 - 30 fingerling tilapia (after a fishless cycle). Am I looking at a trough size/volume for my rafts of 150 - 300 gallons (1:1 - 1:2) as well? Or should I be looking at square feet of surface area (with the commonly known 12" trough depth)? I really have no idea. I also understand that the variables change as the fish grow...my stocking denisty is based on a 1 lb (future fish size) per 5 - 7 gallons. Without guidance, my plan is to attempt a 32 square foot area (one blue DOW insulation board) trough size.

If there are no general rules/guidelines to this, could you please share what size FT you have, stocking density, and surface area of your trough. With enough responses, perhaps we could begin to sense a general ratio or guideline. Or, if you could share a link to a source of this information, it would be greatly appreciated. Thank you for any help you can give.

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Replies to This Discussion

Permalink Reply by Chris Smith on April 16, 2012 at 12:24am

James, the rule of thumb for raft systems that I use is minimum of .3 pounds of fish for every square foot of raft space and at least 4 gallons of water for each pound of fish. That works out to 10 pounds of fish for every 4'x8' sheet of foam. If your fish load gets above .4lbs/sqft then you need to add solids filtration to keep poo off roots of the plants.

Permalink Reply by Max In Missouri on April 16, 2012 at 8:01pm

Let me know when you are ready to build, I am also a new bee and would like to meet others who are into AP. I live here in Waynesville, retired Marine from FLWood. can contact me at 'maxwell.mamona@gmail.com' ... Best of luck to you on your adventures in AP. Max

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Permalink Reply by georgia washington on April 16, 2012 at 9:31pm

Chris, thank you for your response. I really appreciate it because it gives me a starting point from which I can design my system I have to design my system around small fish (fingerling tilapia) because that is how I will order them. As long as I abide by your numbers, it shouldn't matter if the fish are small, right? As they grow, I can increase water volume and raft space accordingly? I plan to start out with a solids filtration from the beginning since I feel like it can't hurt anything. I'm now researching bio-filters since that seems to be the last key element in the system. Again, thank you for your answer.

Chris Smith said:

James, the rule of thumb for raft systems that I use is minimum of .3 pounds of fish for every square foot of raft space and at least 4 gallons of water for each pound of fish. That works out to 10 pounds of fish for every 4'x8' sheet of foam. If your fish load gets above .4lbs/sqft then you need to add solids filtration to keep poo off roots of the plants.

Permalink Reply by Chris Smith on April 17, 2012 at 12:57am

The ratio is pounds of fish to a square foot of grow space. When dealing with small fish it can take more than a hundred to make a pound. In contrast a few of my breeders are 3.5 to 4 pounders each. If you start with enough fingerlings to fertilize one trough you can construct more and bring them on line as the fish grow and can keep up with the grow space. It is best to start with a fish tank large enough for the final grow space using the ratios.

Permalink Reply by georgia washington on April 19, 2012 at 5:47pm

Chris, I've been busy with work so I haven't had time to respond to your last reply. Again, thanks for the clarification. With the ratio you have given, I plan to design tank size, fish density, & trough size according to the future capacity of the tank...and therefore, final grow space area. The limiting factor happens to be the size of my basement. I don't think I could grow much beyond 96 square feet ( 3 4'x8' sheets of foam). Using your ratios, that comes out to about 30 lbs of fish requiring about 150 gallons and 30 1lb fish. Since the fish will be small when I get them, I may wait to add the first raft until after the fish have grown a bit. Thanks for the help.

Chris Smith said:

The ratio is pounds of fish to a square foot of grow space. When dealing with small fish it can take more than a hundred to make a pound. In contrast a few of my breeders are 3.5 to 4 pounders each. If you start with enough fingerlings to fertilize one trough you can construct more and bring them on line as the fish grow and can keep up with the grow space. It is best to start with a fish tank large enough for the final grow space using the ratios.