Introduction: Going Down the Fish Pit

It's been a while since I took the path down into the rabbit hole, or in this case, the fish pit.

At that time, I had just bought an aquarium with a few goldfish for my 5 year old son, who quickly lost interest in this not very talkative pet. Since I've already bought all the equipment, I was reading a lot on the subject, trying to find myself a passion for fish. Through my reading on aquarium maintenance, I quickly branched off on the side path that led me to world of aquapony.

According to Wikipedia, aquaponics is a system that combines plant cultivation and fish farming; plants are sometimes grown on clay balls, which can be irrigated in a closed circuit with water from aquariums where fish are raised.

After I had exhausted my talents as a plumber and gardener, I realized that aquaponics was more than a cultivation system. It was about creating complete ecosystems where the interactions between plants, fish, insects and bacteria were extremely rich and complex.

Creating a balanced ecosystem requires patience and multiple trials, but recreating the mechanics of a natural microcosm brings me divine satisfaction!

For ten years now, I have been experimenting with different aquaponic systems in every corner of my home. From my basement to my bathroom, I have tried to grow tomatoes, kale, chili peppers, lettuce, avocado and a couple of plants that I can't legally name!

This project is my first attempt at outdoor aquaponics. The goal is to build the simplest possible system with the least amount of technology possible.

So, be brave and follow me into the fish pit!



This project consists of a gardening area on rock with a hole in the centre for rearing a few fish. Each day, thanks to a pump and a timer, the water from the fish hole is distributed through a pipe with small holes, trough the pebbles where the roots of the plants filter the fish crap.

The water thus filtered returns to the central hole thanks to a slight slope in the ground covered with an impermeable tarpaulin and rocks.

After a few weeks, a collection of bacteria and insects develops which helps to keep the system in balance.

All you have to do then is feed your fish from time to time and watch your vegetables grow.


What you will need:

- A garbage can or any watertight container at least five feet deep.

- A waterproof tarpaulin

- Pebbles (ideally small enough)

- An old garden hose (it can even be pierced)

- Pieces of wood to belt your system

- A pump for water (It can be a boat bilge pump or a fountain pump...)

- An aquarium air pump

- Silicon caulking

- An electric timer system (optionnal)

- An electrical extension cord

- Something to cover the hole (I have use an old wood box with a glass over it, but you can use only a net)

- 3 to 6 fish (Tilapia are edible and very easy to maintain. Personnaly, I use Goldfish since i'm vegetarian.)

- Plants to grow (Lettuce, Kale, Bokchoi, Eggplant, Squash are easy to grow in aquaponic system)

Tools :

- A saw

- A knife

- A shovel to dig your hole !

Step 1: Setting the Site

Find a spot about 2 m x 2 m and dig a hole in the center, big and deep enough to put your trash can in.

Install pieces of wood to delimit your garden.

Don't despair, this step is the hardest when you're not used to digging!

Step 2: The Garbage Can

Before putting the trash can in place, drill a hole in the top part and attach a piece of pipe to it.

This hose will serve as an overflow if a very rainy day threatens to flood your garden.

Then place your trash can in the hole so that the top of the trash can protrudes about 10 cm above the ground.

Compact the soil around the hole, with a slight slope towards the centre.

Then, cut the upper part of the bin so that the soil is even with the edge of the bin.

Step 3: The Tarpaulin

Attach the tarpaulin to the wooden rim

Once the tarp is in place, put the upper part of the bin back in place.

Cut a small hole in the centre, facing the centre of the bin.

Then cut the sides of the hole so that they can be glued with silicon to the rims of the bin.

The idea of this step is to allow the water to systematically return to the bin without too much loss.

Step 4: The Pebble Bed

On the top of the bin is in place, you need to secure it so it can't move. Put enough pebbles around it to immobilize it.

Now it's time to pump it up! Plug your pump to a long hose (the longer is better, but 12 feet is probably enough)

Then, put your pump in the bottom of the bin and let the hose laying in concentric circle on the bedding. In my case, I pulled the end of the hose out of the system to allow for a wash out at the end of the summer. I put a removable cap on the end.

To prevent the movement of the hose, cover it partially with pebbles.

Cut holes in several places in the hose to try to distribute the water evenly.

Add a little water and test the watering system by turning on the pump. The water should circulate in a closed circuit.

If all goes well, finish filling your tray with pebbles and fill the bin with water.

If the water is very dirty, do a backwash afterwards.

Step 5: Protect Aquatic Wildlife

To protect your fish from being eaten by animals and to prevent too much water from evaporating, the pit hole must be protected.

You can use any material, in my case, I made a recycled wooden box on which I put an old glass.

It allows you to see the fish and to warm the water because tilapias like warm water and I live in a northern country!

Step 6: Automate Your System (optional)

Since I'm lazy and like all automation processes, I decided to install a timer so that watering would be done three times a day automatically.

This step is optional, but I recommend it to anyone who forgets to water their plants.

Step 7: Start the Ecosystem

In order to build an ecosystem, it must be self-regulating. Therefore, there must be a waiting period before putting the fish in the water for several bacteria and microorganisms to take place.

At this stage, you can already install a bubbler in the water and run your system for at least a week before putting the fish in.

Step 8: Fish and Plants

After making sure everything works for a week, it's time to put the fish in the water and plant your plant cuttings.

When choosing fish, goldfish are very hardy, but tilapia are particularly well suited to confined spaces.

Prefer plants that grow well in hydroponics. For my part, I have planted curcubitaceae (eggplant and squash) and kales. But feel free to experiment!

Next, don't forget to feed the fish, since it is their excrement that will serve as food for the plants.

Sit back and watch your ecosystem grow!

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