Fish and plants growing together? It’s not as strange as it sounds. Learn how to build an aquaponics system and what you can grow with aquaponics for health and nutrition.
What is aquaponics?
Aquaponics is one of the most sustainable ways to grow food. It involves a combination of aquaculture and hydroponics in one integrated system. Once you’re set up, there’s very little maintenance or effort required.
The basic premise of aquaponics is that the waste produced by your fish feeds the plants, and the plants clean the water for the fish, producing one continuous cycle.
How does aquaponics work step by step?
This system is based entirely around the nitrogen cycle, which unfolds in the following phases:
- When the fish produce waste (ammonia) into the tank, bacteria break it down into nitrates.
- A pump carries this tank water, which is high in nitrates, to the grow bed where plants are growing.
- The plants draw nitrogen from the water, which both feeds the plants and cleans the water, making it safe to return to the fish tank.
This cycle repeats over and over, with the fish providing nutrition for the bacteria, the bacteria breaking down the fish waste and feeding the plants, and the plants cleaning the water to return back to the fish. Simple!
Why grow food this way?
- Aquaponics uses less water than any other gardening—up to one tenth of the amount used in traditional soil-based gardening.
- Aquaponics requires less time than regular fishkeeping, because plants do some of the cleaning work for you.
- Growing with aquaponics is completely organic. You simply can’t use any harsh chemicals, because they will be fatal for the fish.
- Aquaponics grow beds are usually waist high, reducing the strain on your back while you tend to your plants.
- The amount of time needed to grow with aquaponics versus other forms of food gardening is much less.
Food can be grown anywhere: indoors, outdoors, in greenhouses, even in your bedroom! - Systems can be adapted for your needs—small enough to feed a couple or large enough to feed a community.
Aquaponics design: Which system is best?
There are a few different ways to set up an aquaponics system. The three most common ones are:
Deep water culture set up
The deep water culture system, which is also known as raft-based growing, uses a floating foam raft commonly used in large commercial setups. It allows the roots of the plants to drop into the water and draw nutrients directly from the channel that the water is running through. The water will have been drawn from the tank where the fish are living, and filtered to remove any solid waste.
Nutrient film set up
This method involves drawing the water from the fish tank through a narrow, cylindrical tube such as PVC, which has holes drilled into the top. The roots are then dangled through the holes where they draw nutrients from the water. This set up works for areas without much ground space, because it can be run across walls or hung from ceilings. It can be set up horizontally or vertically, and is great for plants that don’t require any support to grow such as leafy greens.
Media bed set up
In this system, plants are grown in a certain type of media such as clay pebbles, and the media bed normally sits on top of or next to the fish tank. A pump draws the water from the tank, and it then passes through the media bed, allowing the plants to draw nutrients from the water before it is returned back to the fish fully filtered.
This is perhaps the easiest and most commonly used technique for home growers, and the one that we’ll be focusing on in this article.
A tabletop water garden is an educational and productive aquaponics project.
DIY aquaponics in five easy steps
Here’s how to set up an aquaponics system that will allow you to grow your own food at home using the media bed system.
Step one: Put your fish tank together
Just like keeping fish, you’ll need to take into account all the safe practices of fishkeeping. Your fish will require a certain amount of space depending on the species you decide to keep, which will determine the size of your tank.
Depending on the size of the tank you choose, you might be able to get away with using or repurposing a standard acrylic aquarium. However, most people choose to use large barrels or food-grade containers with opaque sides.
You’ll need to set the tank up as you would a normal fish tank—dechlorinating the water and allowing it to cycle for between 4-6 weeks before you add any fish. This gives the bacteria time to build up, ensuring there is enough present to break down the ammonia and nitrites into the nitrates needed to feed your plants.
Be sure to include a pump, which allows the water to be drawn from the tank, to the grow bed, and back again.
Step two: Build your media bed
The media bed can either be built above the fish tank or to the side of the tank.
Your media bed will be the container in which the plants grow. This is also known as a flood table. You can use a large heavy duty plastic tray or a wooden pallet crate. This will need to be built on top of a stand that is able to withstand its weight.
Once you’ve placed the media bed, you’ll need to fill it with your chosen media. Clay pebbles are pH neutral and won’t affect your water. They also hold moisture well. For these reasons, they are one of the most popular types of media to use in home aquaponics.
When you first begin, stick to a ratio of 1:1 between the size of the fish tank and the size of the grow bed, so that the volumes are the same.
Step three: Add the fish
Once your tank has cycled properly, you can add the fish.
There are a number of different fish that work well in an aquaponics set up. Common choices include:
- Tilapia – the easiest fish to grow, simple to care for, and hardy to disease
- Goldfish – produce a lot of waste, so ideal for this set up
- Koi – They grow large and have a high resale value
- Pacu – for those looking for a fancier fish
- Any ornamental fish (guppies, tetras, mollies etc.)
A few less common choices include:
- Carp – reproduce well and are easy to grow
- Silver perch – a fast growing school fish that likes high densities
- Catfish – Don’t have scales so handling needs to be kept to a minimum
- Barramundi – the prince of fish in the aquaponics world
A media bed aquaponics system planted with new lettuce seedlings.
Step four: Add the plants
What plants can you grow in an aquaponics system? Leafy plants tend to grow best. However, if you have enough fish, you might also be able to grow fruiting plants such as peppers and tomatoes.
Here’s a list of what plants grow in aquaponics setups:
- Basil
- Kale
- Lettuce
- Mint
- Watercress
You might also be able to grow these plants if you have a heavily stocked tank and well established set up:
- Beans
- Cabbage
- Cauliflower
- Cucumbers
- Squash
- Tomatoes
- Peas
- Peppers
- Strawberries
It’s best to plant seedlings to give your plants a head start. Place their roots gently into the pebbles, ensuring they reach far enough down to draw nutrients from the water that will pass through.
Step Five: Maintain Your System
Maintaining this set up is pretty simple!
You’ll need to feed your fish a quality diet. You can use a simple flake food and give them the occasional treat. Just be careful that you don’t introduce any diseases to the tank. For this reason, we advise against adding any live food for the fish.
Only feed your fish as much as they can eat in around five minutes, two to three times per day.
You’ll need to test the tank water every week or two to check the pH, ammonia, nitrites and nitrate levels. Ammonia and nitrite levels should always be non-detectable, and the nitrites should be low if the plants are doing their job properly!
The pH should be neutral, between 6.8 – 7.0, which is ideal for the fish, the plants, and the bacteria.
Aquaponics systems typically need to be buffered up (raised) because they’ll drop below 7.0 once the initial cycle has finished. To raise the pH, you can alternate between calcium hydroxide and potassium carbonate, added to the tank in powdered form.
Tend the plants as you would with your normal gardening techniques, but you should find that not as many weeds grow.
We hope this has given you some insight into what exactly an aquaponics system is, and how you can set up your own to start growing food for your whole family, either in your kitchen or in the back yard.
Good luck growing your own food!
