By Claire Mollatt
This article is an introduction to aquaponics with an example of an achievable aquaponic garden that you could set up at home right now! An aquaponic garden would be a way to improve your self-reliance with regard to food and can be achieved in relatively small spaces.
The term ‘Aquaponics’ refers to any system that combines conventional aquaculture (raising aquatic animals such as snails, fish, crayfish or prawns in tanks) with hydroponics (cultivating plants in water) in an environment in which the two systems work together in balance. In normal aquaculture, wastes from the animals being raised can accumulate in the water, increasing toxicity. In an aquaponic system, water from the fish system is fed to a hydroponic system where the wastes are broken down by bacteria into nutrients that can be absorbed by the plants. Then the water is circulated back to the aquaculture system. (ref: Wikipedia : https://en.wikipedia.org/wiki/Aquaponics).
Before getting started you need to understand some of the basic principles of aquaponics.
Principles Of Aquaponic Systems
- It is an ecosystem and requires different species to act together in balance – with some species supplying their waste as a nutrient for growth for others.
- The system helps in closing the loop between waste from the fish creating nutrients for the plants to grow (because there is no waste in nature)
- The nutrients are mostly nitrates for plants once the beneficial bacteria have converted them from urea waste in the biofilter. There may also be phosphates in lower concentrations depending on the type of water you use and the food you feed the fish. These are still useful for plants. Plants also need calcium in small quantities to build their support structures (just like our bones) and they can get this from the water if you have slightly alkaline water, depending on where you live (i.e. it contains some lime/ calcium carbonate). For a simple system, you do not need to do anything really, as long as you feed the fish!
Questions To Ask Yourself Before You Start Your System
- What are your objectives?
- Do you want to do it small or large scale?
- Do you want to sell your produce?
- What resources do you have to build your system?
- How much do you want to spend?
- Do you have the necessary tools (or can you borrow some)?
- Do you need someone help you?
- What is your time-frame?
- How soon do you want to be able to harvest the produce?
- Do you want to harvest plants only or fish as well?
Example Of A Backyard Grower’s Aquaponic Garden
Here is an illustration of an aquaponic garden constructed at home (during the Coronavirus lockdown) in a small space – something you could call a lockdown labor of love!
Materials You Will Need
- Large, leak-free container (e.g. one cubic yard food grade container or similar, old bathtub, old kids’ swimming pool or plastic pool);
- Two other containers – (for example: trash cans) for the two filters to keep your fish healthy. Filters – should be about 25% of the volume of your main tank’s volume;
- Five gallon bucket with bottom cut off (for the radial filter);
- Larger PVC piping lengths – approximately 5 inch;
- Small fish aquarium tank pump – ask at your local pet / hardware store – they can advise on size based on volume of water moving in your container/s;
- UV filter (optional) – helps to kill destructive bacteria throughout the system (which make fish and plants sick);
- Narrower piping connections (e.g. 1.5 inch) with elbows and PVC solvent and cement, (if necessary, depending on where you live);
- Large plastic box and shade-cloth or similar to create a sump (this is optional, dependent on where you are and what plant species you are growing);
- Air stones (pumps that blow bubbles) for biofilter and the fish system;
- A large bag of hair curlers for the biofilter (or other similar objects – for example: small plastic kids’ toys wheels);
- Plastic seed trays or similar – with cotton wool or other material for roots to hold onto;
- Plant seedlings.
Steps For Construction
- The large container is cut into two parts. The first part is the smaller, top layer for the plants and is about one third of the depth of the container. The other, larger part is the remaining two thirds (the container is only cut once) for the fish.
- The smaller part is then flipped and laid across the larger part to create two ponds, one on top of the other. Set up the smaller part with struts so that it is supported, sitting on top of the larger section;
- Cut holes in the container parts to fit the pipes between the bottom level and the top level;
- Fit plumbing attachments between the bottom (where the fish live) to the top level (where the plants float);
- Fit the plumbing attachments between the bottom level and the radial filter;
- Attach plumbing from the radial filter to the biofilter;
- Insert air stones into the biofilter and the fish system and plug them into the power supply;
- The plumbing then needs to run from the biofilter to the sump (where the pump is housed);
- Fit plumbing attachments from the sump to the UV filter;
- Attach the UV filter to the upper, plant tank.
Circulation Of Water.
- Starting from the top smaller section where the plants grow, water flows in a pipe down to the larger part where the fish live.
- From the fish tank it goes into a pipe that sucks water from the surface of the tank and it flows into the radial filter (the first bin).
- In the radial filter, the solid waste settles and clear water flows off the surface into a pipe which leads into the biofilter. (You have to siphon out the sediment from the bottom of the radial filter from time to time).
- The biofilter is where invisible, dissolved wastes (like urea from the fish) are converted into useful nitrates.
- Then from the biofilter it goes to the sump – just a large plastic box with water in it, and some kind of shade-cloth. It serves three main functions – it can house the water pump, it acts as a store for extra water, and it provides extra space for bacteria to do their good work.
- From there, water gets pumped to the UV filter to kill any bacteria.
- From the UV filter it goes back up through a pipe and out into the plant system where the dissolved nutrients are used for plant growth.
What Does The Radial Filter Do?
The purpose of this filter is to get rid of most of the large, visible and solid waste. How does it work? Water comes in through pipe in the center of the inner bucket (which is really a cylinder because you cut out the bottom). The water rises, hits the side of the inner bucket and slows down. As it slows down, all the big particles of waste and any other sediment that is suspended in the water fall to the bottom of the big waste bin. Clean water is sipped off the surface by the outlet of the penstock (the pipe sticking out of the center of the outer cylinder) on the bottom right of Photo 3. You will need to clean the bottom of the bin with a siphon sometimes to stop it from blocking.
Photo 3 – Radial Filter (Photo credit: D. Mollatt)
What Does The Biofilter Do?
The biofilter is essentially a bin filled with lots of biofilter media (surfaces). These are the little black wheels in photo 4 – you can use hair curlers or anything similar. They have a very large surface area to volume ratio which means they provide an ideal place for lots of beneficial bacteria to grow. The bacteria colonize the surface over time and begin to convert ammonia from fish waste and respiration into nitrates (which are used by plants for growth). The biofilter contains two types of bacteria. The first, nitrosomas converts ammonia to nitrites. Then other bacteria called nitrobacter convert nitrites into nitrates which the plants are able to process. Bacteria need lots of oxygen to do their job. This is why in the biofilter you should install one or two air stones at the bottom which will pump through a steady flow of oxygen which the bacteria need to survive.
Photos Of The Aquaponic Garden System
Dos And Don’ts of Your Aquaponic Garden
- Do – make sure you check the whole container for seals and leaks before and after fitting all the pipes;
- Do – take time to figure out how the plants and fish react and adjust;
- Do – remember it is important to adjust your system to contain locally appropriate species.
- Do – keep an eye out for indicators of the system becoming out of balance e.g. algal blooms.
- Don’t – rush; test to get your plants to float properly in the seed trays.
Examples Of Plant Species You Can Cultivate
- Duckweed – for the fish to eat
- Leafy greens for example Pak Choi, celery, arugula
- Herbs , for example cilantro or basil
- Companion species for example, marigolds (to prevent pest infestations)
Examples Of Fish To Use In The System
- Goldfish (ornamental);
- Tilapia or catfish (important to consider size of tanks, stocking density, sex of fish and stress they could be put under in your system’s conditions)
Remember it is important to adjust your system to contain locally appropriate species.
Thanks to David Mollatt for his assistance in providing practical examples, explanations and most of the photos.
For more information follow the link below:
If you have been inspired to create an aquaponic garden – check out the video below for an in-depth explanation!