Tropical Fish and Aquaponics

I have been dabbling with Aquaponics for a while, and seem to be able only to kill several plants.
Aquaponics is to my understanding is that the fish produce nitrates and nitrites through waste in the water, this water is then pumped into grow beds and the plant life extracts the excess nitrates and required nutrients from the water, it then flows back into the tank clean and nitrate / nitrite free. This also helps to keep the PH levels stable.

My dilemma comes in where i am sure the object of the exercise is to keep the plants alive. This is aparently big overseas, with commercial farms running successfully, using tilapia as their fish stock, the fish is sold as a food source as well as the vegetables grown. My interest is in growing crops for my own consumption, not on a lagre scale, but cant seem to get it right.

Has anyone tried this?
Can it be done with tropical fish?

 

Tagging along here... very interesting subject!

 

Hi Jag,

Whilst the idea of recycling the waste products of the fishes back to the plants is a very attractive principle, it is definitely not so easy to get to work.

Tilapia will produce a vast amount of waste which will end up in the waste water to the largest of extents as nitrates. Tilapia can be kept at nitrate concentrations of up to 100 mg per litre. Most fishes as we keep them in aquaria will die from such levels of nitrate, literally. Goldfish, tilapia and barbers can cope with such nitrate levels but all other tropicals cannot. The maximum levels of tolerable nitrate are in the order of 30 mg/litre. If you therefore want to use this water for feeding plants in aquaponics, these levels of nitrates are actually too low for feeding them. In addition, you will definitely need to feed additional other nutrients for the plants to thrive. You would also need to do analyses to determine which nutrients you would need to add. As a result, this whole idea of aquaponics from aquaria is not going to work if you do not have the necessary analytical facilities. I also think that the biggest shortcoming is that the nitrate levels from tropical aquaria are actually not high enough to sustain good plant growth in aquaponics.

Kind regards,

Dirk

 

Thanks For that Dirk, would it work with something like a Jaguar Cichlid? (If I can keep them from killing each other...)

 

I know that Jaguars are a lot tougher than Discus, but I doubt whether they would be very happy at more than 40 mg/litre of nitrate. You apparently need fairly high levels of nitrate before the hygroponics will work, so I still have amy doubts....... But I would admittedly be guessing.

Kind regards,

Dirk

 

Hello,

You have a bigger problem than nutrient levels: warm water. Plants rely on the roots being colder than the leaves/stems in order to pump nutrients back down to the roots. If you use tropical fish, then your roots will almost certainly be warmer than the plants themselves.

You better off setting up the system outside and growing karp/koi or Tilapia.

The fish food should supply all the nutrients the plants need as long as the nitrates are kept high enough. If you have a dog you can always toss a dog turd into the tubs every now and then...

tt4n