Aquaponics?

by John
(Australia)

Have you ever ventured into the awesome world of aquaponics? You've probably heard of it/got a system yourself, but if not it's just like hydroponics except you use fish which provide the nutrients the plants need.

I currently have a small setup using the flood and drain setup with every part bought from a hardware shop (minus air pump and air stones for fish - hydroton was available at the hardware store).

All I've used is:

fish tank 160 litres - so a very small system.
grow beds 30cm deep.
550 litre per hour submersible pump (with a filter sponge thing).
hydroton expanded clay as growing medium
home made siphon system using just hosepipe (I'm about to put in proper siphon system because I found the roots of the plants would grow into the hose causing it to block up!)
air pump with air stones for the fish.
Fish are just some goldfish from a pet store.

Bacteria which grows naturally over time converts the fish waste into nutrients the plants use. A better aquaponics method is the nutrient film technique, which has better results than flood n drain.

Yes, I'm thinking about building a hydroponic system; however, I can't justify the cost of nutrients ($50/bottle in Australia from most places). I would grow outside, of course.

Answer: John- I have read about aquaponics a few times, but I have never tried it myself. One time I got on a survivalist kick and was researching this idea quite a bit....I got my hands on some report that was sold in the back of "Popular Science" back in 1982. It described how a couple of professors were trying to raise a pool of Tilapia and using the waste water to grow a garden of lettuce.

In a survival situation, it would sure come in handy....a source of protein, fresh veggies, and very little worries about where to get the fertilizer from. The biggest problem the guys had was getting the two systems to work in balance with each other. The fish waste was a little on the weak side as a fertilizer, so they chose to grow crops that required less fertilizer strength (ie the lettuce).

They were using a re-circulating system, so adding more fertilizer wasn't an option for them (as higher levels of Nitrogen began to harm the fish). It's been a while since I read the article, but I believe they had a small issue with keeping the pH in balance also....for anyone who has ever grown with hydroponics, this would be a very small problem to overcome.

I suppose if you were going to grow something a little more nutrient intensive, like corn, you would not be able to re-circulate the nutrient solution. Instead, you would probably filter off whatever fish waste you could than add some fertilizer to it. Since the nutrient would be given to the corn in a non-recirculating type system, you would need to replenish the water in the fish tank with a fresh source.

The whole system would be a little more water intensive at that point, but you would still be saving money on fertilizer (especially if you were making your own compost or vermi-compost for the additional fertilizer). Plus, you get to eat the fish!