argylesock says… Here’s an interesting idea. Tilapia (Oreochromis spp.) is a popular farmed fish in the States, and it could catch on here in Europe too. I don’t quite understand the mention of ‘chemical removal’ to get rid of ammonia. Which chemicals? Anyway, I suppose that’s where the nitrate comes from – a valuable by-product indeed. In case you don’t know: ammonia and nitrate are compounds of nitrogen. Nitrogen is essential for making proteins. So all organisms need nitrogen. That’s why crops are sometimes fertilised with nitrate, and ruminant livestock are sometimes fed ammonia.
The Institute of Freshwater Ecology and Inland Fisheries in Berlin is growing tomatoes and fish together, since it has been found that dirty water from the fish tanks can provide nutrients to the tomato plants. The goal is to grow vegetables and farm fish in zero emission conditions.
A few hundred tilapia are being raised in a dozen fish tanks in a greenhouse together with numerous tomato plants. The temperature is kept at 27 degrees Celsius.
The fish are kept humanely, says Werner Kloas, founder of the greenhouse: each tank contains just one school of fish, which is a similar density to that found in their natural habitat. And the tomatoes are planted in mineral wool instead of soil.
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