A couple weekends ago, we decided it was time to start putting together our first aquaponics system. It’s a 500L fish tank with  200L sump pump and a grow bed which is 120x180cm large (30cm deep). Our intent is to grow either catfish or tilapia in it and crawfish in the bottom of the fish tank. The sump will only be used for water overflow and to flush the system. We will eventually add a few more small beds and a few wall pipes too with hopes of adding a bit more filtration since that’s a lot of tank for so few grow beds.

For a quick overview of our system, read this post about our new courtyard aquaponics system. Because it can be rather difficult to find clear, concise information about building an aquaponics system online (although BackyardAquaponics.com is an awesome place to learn and get inspiration), I’m going to try to be as specific as possible so that you can create your own backyard aquaponics designs.

We will be setting up an ebb and flow system but are still working on our siphon drain (more on that as soon as we get it built). Every 3 hours or so, a timer turns on the pump in our sump tank which pumps all the water inside into our fish tank. As the water fills into the fish tank, everything over 500 liters overflows via a hose into our primary grow bed. The grow bed has a slow drain in it which allows water to gradually filter back into the sump tank, at a rate slower than the pump is pushing it out. When the sump is mostly empty, the pump shuts off and the cycle will repeat again 3 hours later.

A general rule of thumb when starting an aquaponics project is that your fish tank should be about the same size as your grow bed. This figure can be tweaked once you have things up and running, if you have large or small fish, etc. But it’s a good place to start and as you learn about how the system works, you can always add more later. It seems that aquaponics systems are never really finished but in a constant state of testing and fine tuning.

We wanted the water to run naturally from our fish tank into the grow bed once the water level in the fish tank rises…so we have the fish tank sitting at a higher elevation. Our entire courtyard actually slopes gradually to one side so it made this layout very easy.

Select a Building Site

Because we already had a small pond in our courtyard which was only an eyesore and safety hazard for our toddler, we decided to build a platform over the pond which would become our grow bed.You can see it toward the middle of the picture below, under the tree and the pipe sticking out of the wall. It’s about 120x180cm around the lip of the pond and 2-3 feet deep. We estimate that it holds about 200 liters of water.

To the left of the tree (but before you reach the door on the left) is where the fish tank will sit. We have several IBC tanks around here and weren’t sure which we would use, but decided to take the tank which was already covered in black pond foil and conveniently located just a few feet away.

aquaponics fish tank

Tools

  • Screwdriver (Rechargeable with multiple battery packs is recommended)
  • Drill with bits which correspond to the screws used
  • Miter saw (You could cut the boards by hand or with other sorts of saws, but the miter is the easiest and cleanest. Or you can have the boards cut for you in the store already if you prefer.)
  • Square angle (to get your corners nice and tight)
  • Bubble level (to make sure your construction is at least remotely level)
  • Radio (because we’ve found that we work a lot more fluidly with music on in the background. This thing has been rained on multiple times, has paint and plaster all over it, the antenna is broken and the thing still works! Best 20 bucks ever!)
  • Saw horses (Not required but recommended. We started without them and needed them once we started adding legs…then wondered why we don’t use those things during every project–standing while you work is so much better than hunching!)

Materials List

Because it’s inexpensive and easy to work with, we decided to build our grow bed out of wood and pond foil but many people select large plastic containers and build stands for them instead. It’s all a matter of your budget and material availability. If you have an old bathtub in your yard or some old trash cans that you’re not using, those will work just as well for various components. Use opaque and dark colored vessels whenever possible so that sunlight will not turn your tanks into an algae farm. Some algae is acceptable and will be appreciated by your fish…a totally green tank that is smothering your fish and clogging up your system is not okay.

The following will build 1 grow bed which is 120 x 180cm large (47 x 71 inches) with 4 stacked legs of various heights (that’s not a technical term, I’m sure, but I will explain what that means in the next construction phase). You will likely want to modify the measurements to your own building site, material availability and preferences.

My advice would be to start with the plywood middle, build the frame for it, then the legs, add additional support and finally put on the sides. Measure all your materials and calculate your lengths carefully. The general rule of measuring twice and cutting once is recommended…otherwise you’ll end up measuring once and cutting twice. 🙂 If you’re not so good with numbers, keep a calculator handy or a piece of paper to work out the figures as you go along…unless you map it all out first and then get started. And what fun would it be to have everything planned out exactly before you start? 😉

Note: Our grow bed is built against a wall so we only have 3 sides covered with decking. If your grow bed will be free-standing, you’ll need more decking for the back side too.

  • (1) 1-inch thick sheet of compressed plywood measuring 105.5 x 165.5 cm
  • (6) 2″x2″(5.5×5.5cm) 3-meter-long boards. Cut to the following lengths yourself or have them cut for you:
    • (2) 176cm (back supports)
    • (2) 165.5cm (frame)
    • (4) 100cm (frame)
    • (2) 72.5cm (foot 1)
    • (2) 36.1cm (foot 1)
    • (2)60.5cm (foot 2)
    • (2) 24.1cm (foot 2)
  • (6) 3-meter-long outdoor decking boards (14.5cm wide and 2.6cm thick), cut to the following lengths:
    • (4) 180cm (front)
    • (9) 105cm (sides)
  • 1 box 5×70 screws plus other larger screws we had around

Because I’ve yammered on so much about this project already, I thought it would be best to break it down into multiple parts. Come back tomorrow for part 2 when we really get down to work.

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