When you are designing or building Aquaponics system you will be considering 2 area?

The tank/s for the fish and the grow bed/s for plants?

I have create this post to help you understand the difference between Fish density and Fish capacity, which in turn I hope will assist with your design of your Aquaponics system?

As always after ready my bit of Ba Ba Ba, I would hope you will really research Fish density and Fish capacity, more in-depth?

Fish density and capacity are so different and it is important to understand the difference when building an Aquaponics system.

Fish Density is basically; the number of fish your tanks will hold without killing them.

Fish Capacity is basically; the Total weight of Fish that your Bio-Filter can handle.

“Fish Density” is measured by the amount of Kg of fish per Cubic/m of water and this will be determined by

• The type of fish, as all fish have their tolerance of amount of other fish around them.
• Your tanks sizes govern the cubic/m of water for your fish

Let’s look at this stocking rate for Tilapia

Nile Tilapia, 77 fish per 1 cubic/m @ 450 to 500grams = 38.5 Kgs

Red Tilapia, 154 fish per 1 cubic/m @450 to 500grams = 77 Kgs

Density: Now if you have 10 cubic/m of water that’s a 10,000 litre Tank you could assume that you can grow 10 times this amount of Fish indicated on the stocking rate above?

So you can stock fish to the highest stocking rate that your water capacity will allow BUT can your system manage the filtering of this density?

This is why Density is different from Capacity;

Capacity: is how much your Biofilter will cope with the amount of fish in a tank because your Bi-Filter is handling the Ammonia that your fish produce.

We design our systems around the Biofilters and then build our fish tank sizes around that.

We work on the formula of;

10kg of Fish (not the number of Fish) produce about 7.5grams of Ammonia and 0.6 grams of Ammonia can be converted by 1 sq./m surface area of our Bio-System.

“Fish Capacity” is measured by the converting capacity of your Bio-System to deal with the ammonia that is produced by the Kg of Fish you wish to grow.

Example;

If your biofilter (7.5gms x 40kg = 300 grams of ammonia) can deal with 40kg of fish, that means your biofilter needs to have 500sq/m of surface area.

Note; Read my post on Biofilter

Do your search and get your head around the importance of the Bio-Filter because there are three things you grow in your Aquaponics System;

1. Fish,
2. Plants and
3. micro-bacterium.