How to Make a Mini-Aquaponic System for $20

Upcycle a 5 gallon water container to become a mini Aquaponic system.

My most popular post (so far) describes how to convert a standard 10 gallon fishtank into a Deep Water Culture Aquaponics system for $50. (The materials cost about $35. I rounded up since I needed to buy a hole-cutter and also gas to drive to a few stores.) I built it to be plastic-free and portable. It worked well, but wasn't ideal for transporting to and from my Aquaponics presentations. Glass is considerably heavier than plastic and susceptible to leaking and cracking. Water weighs 8 lbs/gallon, so that whole system weighs about 90 pounds.

I love the scalability and simplicity of Aquaponics. Motivated to build a smaller, lighter, sturdier, and less expensive system, I did some research and found the video below on Youtube. It uses a recycled 5 gallon water container. To keep it simple, I decided to modify the design a little and eliminate the vertical PVC structure with hanging plants. All my plants grow in the growbed.

This system experiments with drip irrigation, similar to Nutrient Film Technique (NFT) and uses the air pump to lift water. This system is super portable and uses only 2 watts of electricity from a simple $5 aquarium air pump (which was the most expensive component). This time I didn't have to buy anything since I already had all the materials. I estimate the whole system costs about $20, and it costs even less if you use recycled materials.

Materials/Tools: Hacksaw, knife, small aquarium air pump, about 7-8' airline tubing, airline "T" connector, one-way air pump check valve, 1 gallon bag of inert growbed media (growstone, hydtroton, expanded shale, or pea gravel), 4" inch PVC pipe, a handful of small office clips, and a twist-tie.

How to put it together:
Find a 5 gallon (18.9 liter) plastic water container and rinse it out. If it has a handle, even better.

Take a hacksaw and cut the top off just above the handle. Then cut off the bottle neck. Keep it, you'll need it.

Invert the top part into the bottom and the neck through the hole.

The bottom becomes the tank and the top becomes your growbed. You'll feed your fish through the stem.

Cut holes in the bottom two inches of PVC pipe for drainage. Center it inside the top part. You can use a hacksaw to cut parallel holes across the bottom couple inches of the PVC or, use a drill to make the holes like I did. You don't need to drill this many holes; I had already drilled this PVC for a different system, so I used it.

The PVC piece becomes your gravel guard.

I used a sample gallon bag of Growstone made in the U.S.A. from recycled glass bottles. It's extremely porous and incredibly lightweight.

Hold the gravel guard down and add the stone around it evenly.

Connect a small section of airline tubing from the air pump to the one-way check valve. The valve helps prevent risk of electrical shock from water backing down the tube into your air pump, but it will also restrict the flow of air from it. The arrow on the valve indicates the direction of the air from the pump.

Make sure the arrow on the valve points away from the air pump.

From the check valve, connect about 3' of aquarium tubing into one of the top ends of the "T" connector.

Important: the "T" connection piece must stay at the bottom of the fish tank, otherwise the air pump cannot lift the water through it and the system won't function correctly.

I ran the airline tubing through the hole in the handle of the water container to help keep it in place.

Connect about 4' of tubing from the middle connector for your water/air lift to the growbed. I added a few inches of airline tubing to the bottom connection and anchored it to an aquarium ornament. 

How to lift water with an air pump.

My aquarium ornament conveniently had a perfect sized hole in the bottom that was designed to connect airline tubing to push bubbles. (With the "T" connected, instead of pushing air through it, it now draws water from the bottom of it.) You can also use a rock to anchor the "T" connection to the bottom of the fish tank. Make sure the end stays open so it can suck water through. 

Take a twist-tie and make a loop above the level of the growbed in the section of airline tubing that runs from the check valve down through the hole in the handle to the "T" connection. Connect it to an office clip on the rim of your growbed. This is another precautionary measure that will help prevent electrical shock if water accidentally backs up through the hose.

Take the end section of your water/airlift hose and form a circle around the circumference of your growbed. Poke about six small holes every few inches of the airline. Make the holes just big enough for water to drip out. Clip the airline underneath the top rim of the growbed to secure it in place.

Fill it with water and stop an inch or so below the bottom of the growbed. Fish food needs to fall into the water from the hole in the middle of the growbed, so don't overfill. Plug in the air pump. Add some small plants below the dripping water. Make sure to rinse any dirt from the plant roots beforehand. I transplanted aloe, mint, a small Jade plant, strawberry, and a rosemary shoot.

You'll want to add some fish, of course. Pick varieties that will stay small since there is only 2 1/2 gallons of water in the system. I am considering adding cold water snails, crayfish, fathead minnows, or some other variety that won't grow too large and won't require a heater. Here's a short video of my system in action.

I haven't added fish to my system yet since the water is just beginning to cycle. If you are new to fishkeeping, check out these tips for cycling your new tank.

For additional water filtration and aeration, I am considering adding a small homemade sponge filter like the one from the Youtube video below. They work great.

Post comments and questions!