Aquaponics 101 – A Productive Season

A very Happy New Year from Synaptoman and Co. I trust that you are all well rested and ready for what I believe will be a very eventful and interesting year.

The Knysna Aquaponics exercise has gone from strength to strength, and my system is now almost fully cycled. What I have learnt is that aquaponics is very much like the chicken and egg scenario. Without ammonia to get the system started, you basically don’t have a system. With ammonia in your system, your fish suffer. Without boring you too much, let me briefly explain the portion of the Nitrogen cycle that affects us in Aquaponics.

The fish produce ammonia when eating, directly from their bodies, and in their excrement.

Nitrosomonas is a bacteria responsible for changing this ammonia to nitritre.

Nitrobacter is another bacteria responsible for changing this nitrite to nitrate.

Ammonia and nitrite are harmful to fish, nitrate substantially less so. Also the plants are able to take up this nitrate as nutrients.

Both of these bacteria are relatively slow growing, with nitrosomonas growing first. Both of these bacteria live in that dirty water clinging to the gravel at the bottom of the grow beds.

To monitor the progress of these bacteria, we test the water for ammonia, nitrites, nitrates and pH with a common aquarium test kit, and compare the colour to a colour chart, as follows;


From this test we have readings of;

Ammonia 0.8 (this is low, but we’d like it to be zero)
Nitrite 0.25 (this was dangerously high, but has come down nicely, aiming for zero)
Nitrate 50 (this is now going up)
pH 7.5 (acceptable)

From this test we can see that both bacteria are growing. The elevated nitrate means that the bacteria are doing their job, but there are insufficient plants to take up these nitrates. More grow beds and plant growth are thus required.

Set out below an image of the system as it looks now;


I have also built a smaller aquaponic system for my goldfish in the pond with a submersible pump and a single grow bed. The day after I finished I noticed lots of thrashing and chasing around in the pond and realised that the goldfish were spawning furiously, and rushed to get some shade cloth in the pond to collect the eggs as they immediately eat them. I have placed them in a safe cage in one of the Tilapia tanks, and they should hatch out any day now. This is what newly fertilised goldfish eggs look like.


Of all 450 Tilapia fish collected I have now only lost one fish, who decided to jump out of the tank the night before last. This does save me culling one to check stomach contents etc. He as 100g and 200mm in size. Gills were a nice colour and stomach contents consisted of some algae and a few pellets. All good. This is what the poor bugger looked like.


I am pretty happy with my water quality now, so I have ordered 50 female brood fish, which I will probably collect in a week or two.

Be Good


Democracy is two wolves and a lamb voting on what to have for lunch.  Liberty is a well armed lamb contesting the vote.

Benjamin Franklin

5 Responses

  1. […] 4.  Measure levels of ammonia, nitrite, and nitrate […]

  2. Hi
    I’m really interested in aquaponic, and I want to run a small aquaponic as well. I really need commend as well as lessons about it; therefore, that’s really good if anyone can help me!

    • hi chandara, i have been running a small scale setup in my backyard for the better part of a year now , if you need any help or advice on setup and maintenance feel free to send me a email, and i will gladly answer your questions. contrary to popular belief you can have a setup as small as 1gal you just have to maintain it better . looking forward to hearing from you and helping you on your way!

    • go to

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