Backyard Aquaponics on a Budget

So, what is aquaponics? Aquaponics is a system that combines conventional aquaculture with hydroponics in a symbiotic environment. Basically, it's a system for growing plants and fish for food. Plant wise, it is similar to hydroponics, however, it is done outside (so no fancy lights needed) and instead of using chemicals to feed the plants, you raise fish and/or freshwater crustaceans such as yabbies or marron in the water tank, and good bacteria converts the fish waste into nitrates which are then used by the plants for nutrients.

A pond pump is used to pump water from the fish tank up to the grow bed, in which expanded clay is used as a grow medium for the plants while serving a double purpose of filtering the water for the fish tank. The expanded clay also provides a large surface area for the good bacteria that are essential to the system to live on.

I built our backyard aquaponics system on a budget. You'd be amazed at how much you can save by salvaging materials destined for landfill, sourcing second hand items, channeling your inner MacGyverette (or MacGyver), repurposing unused items, and thinking outside the box...

Visit any fish farm or hydroponics store, and you will see the purpose built tank and grow bed kits for sale, with prices starting around a few hundred and increasing along with size and features. If, like me, you don't have mounds of spare cash to splash, but you would still like to give aquaponics a go, improvise.

We currently have 3 systems set up. The largest, pictured above, consists of an old 8ft diameter, 24inch high, hexagonal, framed, above ground swimming pool (a Clark Rubber $100 special 8 years ago. Similar available at Kmart and Big W for between $100 and $300 depending on size and season specials) that we had not used for swimming for a few years as my kids had gotten "too old" for it. We set it up without attaching the supplied water filter, rather using 2 pond pumps for circulation, both sourced on gumtree for under $20 (although available new at Bunnings and other stores, for around $150 to $300 depending on size. Bigger is better).

The grow beds I made by creating 2 platforms, each using two sturdy jarrah patio timbers laid above the pool to hold the containers securely while allowing space for the central drainage holes to drain freely straight back into the pond. One platform is resting directly on the frame of the pool, the other I built a small brick wall either side of the pool to support the beams and raise them higher than the other platform.

The grow bed containers are just plastic tubs from Bunnings and Red Dot. The most expensive were $4 each. The white flexible tubs with handles are proving to be the most durable and the easiest to work with. The colored tubs are not flexible and can crack easily if due care is not taken.

The irrigation system is a patchwork of garden hose and clear vinyl tubing. In hindsight, the garden hose is the better option as the clear tubing encourages algal growth and thus require more maintenance than the garden hose tubing.

For the drainage systems, for the medium (pebble) barrier, I used some old PVC pipe that I cut slits into with a hacksaw, using a box cutter to smooth the edges afterwards. No need to buy a $25 drainage kit for each container. For the drainage, I just used old pop up sprinklers with the guts removed screwed onto a joiner on the other side of a hole cut into the base of the container.

When I ran out of sprinkler heads I just started using vinyl tubing screwed onto a retic pipe joiner. A little piece of plastic coated wire mesh snipped to size stops any stray pebbles blocking the drainpipe...

I use expanded clay (mixed with gravel in a few as I ran out of the expanded clay) in the grow tubs for the aquaponics (washed well 3 or 4 times). Expanded clay pebbles can be bought at Bunnings and other garden supply stores, averaging $40 for a bag of it. This stuff is great as it can be washed and reused many times.

You want to have the surface level of the pebbles an inch or two above the water level to discourage algal growth. Let the system run for a few weeks to stabilize and allow the colonies of bacteria to establish before adding plants, and start with just a few fish and/or yabbies.

Once the water is nice and consistently clear, you can start adding plants. I wash most of the soil off the roots of the seedlings before planting them.Make sure the roots are nicely covered by the pebbles and sufficiently submerged below the water level.

I also add a handful of worms from the worm farms to each grow bed which keeps on top of any fish waste and vegetable matter from the pond that gets through the pre-filter and accumulates in the stones. The worms also keep root systems healthy by eating old root fibers, meaning the roots stay nice and white and healthy. Surprisingly, the worms in the stone filled grow tubs are VERY healthy. I thought they'd get squashed or drown, but this is not the case.

This photo (below) shows our version of the popular "chop and flip" set up in which an IBC (Intermediate bulk container) is used for both the water tank and the grow bed.

IBC containers can be sourced second hand or new. Second hand containers go on Gumtree for anywhere between $20 and $150. Be sure to clean them out thoroughly before use. I used a pressure washer to clean ours out.

A common mistake made by beginners is buying the fish too early. It takes at least a couple of months for the good bacteria to establish in the system, and adding fish too early can result in a problem common to all forms of aquaculture: excretions from the aquatic animals being raised can accumulate in the water, increasing toxicity.

Ensure system health by monitoring PH levels. The ideal level is midway between the optimal levels for both plants and fish, namely around 6.7.

I also recommend using a pre-filter kit on your pumps. The removable sponge filter will need cleaning anywhere from every day to weekly, depending on fish and crustacean population and size rates. Clean the sponges in a container of water and use the dirty water to feed any plants and veggies you have growing in pots or in normal garden beds or raised beds.

Half the fun for me has been the process of figuring it all out.

This will get you started, but the learning never ends. Enjoy.