Did you know that a fish tank can provide a rich source of fertilizer to feed to your plants? As someone who keeps a medium sized freshwater fish tank in his living room, and also has a reasonable collection of small houseplants (I even grew a few tomato and beetroot plants last year) this was a real revelations to me. All of that filthy water I had been throwing away is actually a valuable resource that I could have been using! I'm not one of those eco-warrior types who are obsessed with recycling or organic food, but I do like to be able to make use of things that I have lying around, especially when it saves me money on something that I had been purchasing (like plant food, which I have now stopped buying). Its also nice to have something a bit more natural and to therefore be less dependent on products which often contain artificially produced chemical components.

It is obvious really - other animal wastes and even human waste is used as fertilizer, so it stands to reason that you can do the same thing with fish waste. It is even conveniently dissolved in water to make it easier to handle and use! Having discovered this fact just a couple of months ago, I decided to read up a bit more about the subject, and this article is the result of my research. It is not intended as an in-depth or technical guide, but rather as an introduction to an interesting subject aimed at complete beginners.

To go somewhat beyond the simple definition I have given so far of aquaponics as 'feeding fish poo to plants', a more precise definition would be to say that it is the practice of raising fish and plants in a symbiotic relationship.

The History of Aquaponics

Aquaponic practices actually have a very long history of use. The ancient Aztecs are thought to have been amongst the first to use the technique, by dredging canals for waste water to irrigate their crops.

For many centuries, some rural communities in South East and East Asia have also engaged in aquaponics, raising fish in the paddy fields where they also grow their rice crops.

The practice has only recently been 'rediscovered' and researched in a more technical and scientific way, however. The first modern Aquaponics techniques were developed at the North Carolina State university in the United States during the 1990s.

Closed Loop Aquaponics

Not only can fish provide an excellent source of nutrients for plant growth, but the plants themselves can perform a useful function by helping to filter and clean the water, which can then be fed back into the fish tank. This can be used to create a self-sufficient 'closed loop' system - a complete independent ecosystem capable of sustaining itself with little outside intervention. This leads to a reduction of 90% or more in the water requirements for growing the plant crops, as well as providing organic and free fertilizer.

Modern Aquaponics Systems

Any crop which can be grown using hydroponics can also be grown using aquaponics, and there are many similarities between the two systems. The plants themselves are often grown on solid or spongy grow media, rather than in soil, as this allows for a greater degree of control and makes it easier to create a system which filters the water sufficiently to feed it back into the fish tank.

At its most basic level an aquaponics system would only need a fish tank, a pump, and a growing bed which would usually be located above the tank.

To improve the efficacy of the system, the right kind of bacteria need to be encouraged, in order to convert the ammonia from the fish urine into nitrates, which can be more easily absorbed and used by the plants. This can take place in a dedicated component of the system, but is often encouraged within the water of the fish tank itself (it will actually happen on its own to some extent, within the tank). This can be done using a special film attached to the sides of the tank.

Both the plants and the fish will require oxygenated water, so method of doing this is usually required.

Some systems do not even require the use of pumps to move water - instead they use floating grow beds which are just placed on top of the water. And some fish are even able to eat the roots of the plants growing above them for their own nutrition, creating a truly symbiotic relationship!

Most aquaponics systems are housed indoors, which means that they also need to have appropriate grow lamps to enable the plants to photosynthesize.

Aquaponics At Home

At its most basic level you can just scoop some dirty out of your tank when it comes to cleaning time and use it to water your plants. That's actually what I am doing at the moment, until I can find the time and money to set up something better. This is obviously not the most effective method, as there will be too much ammonia and not enough nitrates (that ammonia shouldn't actually be harmful to most plants, especially not just once a fortnight when you clean your fish tank, but its not as good for them as the nitrates).

If you want to set up something more professional, you should be able to get everything you need from a hydroponics retailer. You will have to be a bit creative, however, as there are very few good quality guides to building a DIY aquaponics set up on a domestic scale. You can buy kits, but most of them seem to be aimed at professionals within the agricultural industry. You can also buy a small pre-made 'aquafarm' big enough to keep one or two small goldfish and grow a few flowers or herbs from a company called 'Back to the Roots', which was funded via Kickstarter last December. They describe their product as a 'self-cleaning fish tank which grows food', and everything you need to get started is included with each purchase.

Category: Agriculture

QR Code
QR Code aquaponics (generated for current page)