Backyard Aquaponics
A place to discuss aquaponics

Besides seasol can anyone give me any tips for fertilisers and additives that are suitable for aquaponics systems that won't harm fish.

depending on your setup you can put bood & bone (not too much) sprinkled on the grow bed and gently water in.
Also the Yates B&B with potash. Good for tomatoes. Sulphate of potash can help.

If you need nitrates (usually only young system) - you can add a little power feed direct to grow bed or charlie carp.
You also have the option to foliar feed - in which case you can use most things in moderation.

Also depends on system pH. eg. Potassium Carbonate (KCO3) and Caclium Carbonate etc is useful if you have a low pH system.

Some people have used organic supplements like 'tea bags' etc.
But mostly in AP you are chasing elements like potassium (K), Iron (Fe), magnesium, sometimes Ca.
(the ones that most plant deficiency charts show)


Mostly you need to stay away from supplements that are high in nitrogen and phosphorous (N & P).
After that copper, zinc and some metals that are toxic to fish.

with supplements don't use too much of the same thing and make sure what you use is applicable to your pH.
eg. sulphates etc can build up over time.

[edit] as a rule however you should not need to supplement too much if you use a high quality feed and have a reasonable level of stocking. It is not hydroponics so definitely less frequent and mainly when plants suggest you need it. You may need to supplement a little bit more when a system is low stocked, small fish or under stocked.