Backyard Aquaponics
A place to discuss aquaponics

Hi guys,
First of all I love the forum, it is very informative.

I'm struggling with one question for a long time now.
I'm designing a commercial passive greenhouse with an aquaponic setup and need to figure out the size of the fish tanks and filters (+ mineralisation tank).

So first of all, the setup.
We will be growing lettuce (floating raft) and have tilapia for fish.
The grow beds are 12 x 2,5 m (30 cm deep). There are 10 of them plus one for starting plants and one for testing. So one bed is 30 m2. Totally 360 m2 of growing area.
The production set will be around 5500 lettuces per week.

I have read the UVI Aquaponic setup which specifies the ratio as g/m2/day and the concrete number was 60 g/m2/day for lettuce. Which will add up to 21,6kg per day.

Then there is a paper by Aquaponic solutions Wilson Lennard PhD http://www.aquaponic.com.au/Fish%20to%20plant%20ratios.pdf, in which he sets an example of 1kg of fish feed will support 1500 lettuces. This will translate to my setup as 3,7 kg of fish feed.

This is too much of a difference. I know he explains that it is his specific formula. But still.
I hope someone can help me figure out the correct ratio or better yet size of the fish tank and needed filters out of that.

Thanks guys.

Welcome to the forum. First let me say that you are going in the right direction if you follow the aquaponic principles that Rakocy and Lennard have laid down. But as you have noticed, their philosophies differ somewhat.

Do you know the fish biomass difference between their two systems. I would think Rakocys produces an equivilant amount more of fish (fish biomass/g of feed total). The main difference is that Rakocy discharges all the settleable and suspended solids, while Lennard collects solids into a mineralization tank and adds them back to the system in dissolved form. Therefore, he can support a higher biomass of plants/gram of fish feed. Hope this helps and good luck.