14 June 2007

Aquaponics in the backyard

I thought I'd give those interested in our aquaponics system a bit more info. Aquaponics is an intergrated system of growing fish and organic plants, our plants are vegetables. Our system is situated on the back verandah and is connected to the electrical plugs in a little brick shed closeby.

We have a 3000 litre fish tank (see above) that contains a submersible pump. Water is pumped up to the two grow beds above that are filled with gravel and vegetables. The water contains all the fish waste (ammonia, nitrates etc) and when it is pumped to the grow beds, it fertilises the plants organically. The water then falls back into the fish tank as clean water.

This is from:
How Does it Work?
In aquaponics, the nutrient-rich waste-water from recirculating aquaculture provides a food source for the growing plants and the plants provide a natural filter for the water the fish live in. This creates an ecosystem where both plants and fish can thrive. Aquaponics is the ideal answer to a fish farmer’s problem of disposing of nutrient rich water and a hydroponic grower's need for nutrient rich water.
The key to a successful aquaponic system is a healthy colony of beneficial bacteria. These bacteria convert fish waste into nitrate and other elements which are used by plants as they grow. Without the bacteria, ammonia and nitrite levels, which are toxic to fish and plants, would quickly rise.
Aquaponics can be used to produce large quantities of food in very small spaces in an environmentally friendly way.

This is our fish tank after it had been running for about a month.

We have enough room to humanely farm about 100 silver perch, a fish that is native to Australia's Murray-Darling river system. We chose silver perch as they're a good beginner fish, they taste good and can tolerate a wide variation in temperature.

You can see the baby perch peeking out of the plumber's pipe
we put in for them to hide in.
These are the heirloom Brandywine tomatoes riping in the winter sun. They were planted in late March. The photo was taken this morning.

This is a marketmore cucumber, another heirloom vegetable.
It's using the celery as a growing support.

Aquaponics is a brilliant way to grow edible fish and organic vegetables and fruit in the same small area. Once your system is set up and has matured, you'll be getting organic produce simply by feeding the fish. Imagine that, no fertilising, no watering, no weeding. As a lifelong vegetable gardener, I think that's a pretty good way of growing food.
BTW, for those of you who are worried about excess water use, our system is set up entirely on rainwater we harvested from our roof. You do need to top up a little water when it evaporates off and if you have problems with water quality you might have to change some of the water, but when the system is running well, you use very little water, much less than in a conventional soil garden.

If you're thinking of setting up a system, you'll get all the help you need here:


  1. Thanks Rhonda Jean for this post, since I read this here yesterday, I haven't been able to get it off my mind.

    I am adding a link to you from my blog. I think you have some great info!


  2. thank you, P. I just checked out your site. I LOVE that compost tumbler. : )

  3. Thanks Rhonda jean.
    Have you eaten any of the fish from an aquaponics system before or will this be your first batch? I am curious about the texture of the fish having so little moving area? I have eaten farm raised trout and salmon and have found them slightly mushy (for lack of a better description; just not as firm fleshed as wild.) I saw a salmon tank once that helped to raise salmon to be introduced into the wild, they had their inflow pipe cocked at an angle to cause the water to create a slow whirlpool. The fish naturally swam upstream, thus building the muscle that would help them in their lives in stream. Could be an interesting idea huh?

    Forgive my persistent rambling on this, I'm always trying to rethink things or find a solution to things. Of course that's how I ended up with the composter though isn't it?

  4. I have never eaten farmed silver perch. Joel, who owns the backyard aquaponics site, says they taste good but need to be purged before killing. You do that by putting the fish in a tank of clean water for a few hours.

    Perch are not migratory fish and unlike salmon and trout don't swim upstream. Maybe that is the difference but I really won't know until we eat the first batch.

    I think it also depends on what the fish are fed. My hope is that I can make up an organic mix that's easy to prepare and the fish like. I'm hoping to use my worm farm for that.


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