How to run successful aquaponic system

Aquaponics is no nuclear physic but accelerated nitrogen cycle which serves as a driving mechanism for plants growth. There are several principles that are important to keep in mind in order to avoid the fish to die during running this cycle.

In the beginning, I need to say that most of forthcoming ideas and rules are not my own but they come from the internet. I run myself a small aquaponic system in an IBC container for one season so far and I definitely do not consider myself to be an expert. :)

1) Proper amount of feed material per growth area

The calculation of maximum productive potential of Větrušovice's aquaponic farm is described in separate article. In general – 1 square meter of growth area can absorb 60g – 100g fish food. It is recommended to feed rather carefully – excessive feeding can cause more damage than insufficient feeding.

The daily amount of fish feed material is determined by percentage of their weight, which differs by fish type and age.  I used 2 % of fish weight as a feeding dose to simplify the calculation of growth area to number of fish that will plants need. Fish should eat the dose in roughly 20 minutes. If you find pieces of feed in the tank after 20 minutes you should lower the feed dose for next feeding.

2) Keep the daily feeding dose constant

It is important to keep the daily dose of nitrogen in fish food same to ensure the stability  of the system. This keeps colonies of desirable bacterias strong which helps the ammonia oxidize to nitrites and subsequently to nitrates which are absorbed by plants' roots.

But how to keep the dose same while fish grow and increase their weight? There are two methods. One is separate farming of fish – for example using three fish tanks, each one with fish of different age. If you are going to breed carps up to 12 months you will have three tanks with carps aged up to 4 months, 8 months and 12 months. This process is usually used by commercial aquaponic farms because it allows quick fishing out of big number of fish, that are the same weight, and its sale.

However, I chose the other, rather domestic method for our farm. You breed all fish in one tank where big fish are taken out while the others are still growing. You put one kilogram of new fish for every kilogram that is fished out and the feeding dose stays the same.

3) Replenish the system with calcium, potassium and iron

There are 13 substances that is essential for healthy growth of plants, however, fish food provides the system with only 10 of those. The rest 3 need to be added separately to maximize the potential of whole system. Experimental farm in Alberta, Canada used potassium in form of potassium hydroxide and calcium in form of  calcium hydroxide. 

The iron was supplemented in chelated form which is easy to absorb. The same form is used for diet supplements in pharmacies but I will try to get an industrial packaging. Because chemistry of water is really important I have scheduled some laboratory exercises.

4) Air is important

Due to necessity of enough air in the water that fish, plants and bacterias consume you need to install an air pump in the pool. The satiety should be about 5mg oxygen to 1iter of water. I will use an Air Lift method for my aquaponic farm. This technique allows water circulation and oxidation at the same time. You can find out more about Air Lift in separate article here.

5) Remove solid residue of fish food and excrement

Although it could seem that more solid particles left in system should help better nutrient distribution it not quite like that.  The concentration of nutrients for healthy growth of plants is about 0,025% in clean water. Solid particles attach to roots and consequently reduce the ability of air absorption. It can easily evolve into rotting process that damage the roots and can eventually cause fish suffocation.

Variety of filters and washers are used for removal of solid particles. For my aquaponic farm I have designed a washing shaft with two overflows that will collect sediments that will be flushed out on regular basis.

6) Watch the pH

pH, also known as acidity, affects many chemical reactions inside aquaponic system. The process of nitrification, where ammonia dissolves to nitrites, runs best at pH 7,5 while at pH 6,0 it almost stops. That causes the aquaponic system to fail, water begin to accumulate ammonia that is toxic for fish and eventually kills them. Acidity in aquaponic system tends to grow over time due to intensive activity of nitrificating bacterias.

Acidity also affects intensity of nutrients dissolution in water (e.g. slow sugar dissolution in water-vinegar solution). Ideal pH for dissolving nutrients is 6.5 and lower. Different requirements for nitrification and nutrient dissolvability forces us to compromise and keep the pH at 7. Higher pH causes nutrient to condense and consequently plants will suffer. Lowe pH causes accumulation of ammonia and resolves in killing fish.

It is best to use potassium and calcium hydroxide to decrease the pH. I will use this method to keep the pH at 7 and supply the system with calcium and potassium at the same time.