A guide to setting your own aquarium aquaponics system
Intrepid aquarists that want to do something special with their tanks will be glad to know that turning an aquarium into a small-scale aquaponics system is not quite as hard as it looks. It may seem complicated, but the underlying science of the matter is stuff that any aquarist should already be comfortable with: the nitrogen cycle, the symbiotic relationship between fish and plants, and the health benefits they offer one another.
If you have kept a planted aquarium before, you already know that the nutrient-rich water of the tank is perfect for plant growth. Aquaponics is just a system by which you can maximise that growth and raise some terrestrial plants while you’re at it. A successful mini aquaponics system can provide you with delicious fresh vegetables, herbs, and spices while giving your fish excellent quality water.
Making your aquaponics system self-sufficient
There are several different ways to construct an aquaponics system, but this article will focus on ways to make it as self-sufficient as possible. Self-sufficiency will cut down on maintenance, but may also deliver smaller yields in return. If you would like to grow large quantities of vegetables, you will need to invest in a more robust set up.
The system described below is a perfectly suitable beginning aquaponics setup that focuses on minimising the need for strict maintenance. If you would like to improve it once you get it up and running, you can invest more time and effort into producing larger yields.
An aquaponics syste has all the hallmarks of a Walstad aquarium. With the closed ecosystem and natural substrate of the growbed. The fish providing nutrient manure for the plants and the plants filtering out toxic waste products from the fish, ie nitrogen recycling. However, where the system differs is that there is a nutrient export. The plants when they get harvested do not recycle back into the system. In the medium to long term there will be a deficiency of minerals that the plants are taking from the water. You will have to occasionally replenish these nutrients.
What you need to build your aquaponics system
Your aquarium tank, of course
- A gravel substrate, 1 kg for every 20 litres of water in the tank
- A small circulation water pump
- 1 metre length of plastic tubing, that will fit on the outlet of your pump
- An air stone
- An air pump matched to your tank’s size + (optional sponge filter)
- Another 1 metre length of plastic tubing, sized for the air pump outlet
- A growing medium, pea gravel, perlite, and peat moss work well
- A plastic grow bed, ideally the same size as your tank and sitting on top of it with a depth of 7 – 20 cm
- actinic lights for your plants
- Ordinary aquarium lighting for your fish
- A pH testing kit
- A drill
- A heater for the fish
- And some fish
How to setup your aquaponics system
One thing you must bear in mind is the height and weight of the whole system when it is all put together. The height will be the height of the aquarium plus the height of the grow bed plus the height of the lighting system above the grow bed. So either obtain a shallow aquarium of make sure there is plenty of room above the aquarium for access.
The first thing you will need to do thoroughly wash your gravel substrate and line it along the bottom of your tank. Then drill tiny holes (3–5 mm) into the bottom of your grow bed with an even distribution, every 5 cm or so. This will let the water drain into the aquarium. Drill a larger (10–12 mm) hole into one of the corners of the bed so that the water pump tubing can pass through.
Now you can place the water pump inside the tank and cap the top with your grow bed. Insert the water pump tubing through the hole you made in the grow bed—leave a little bit of extra tubing to loop around inside the grow bed and cut of the rest. Fold the end of the tub over and seal the folded tube with tape.
Once you have this done, puncture tiny holes every 5 cm in the looped section of tubing in the grow bed. You may now fill your grow bed with your peat moss or pea gravel up until you cover the tube. This is the basic form of your aquaponics system.
Now you can focus on the aquarium: fill it with water and plug in the pump. You should see the water pumping into the grow bed and trickling down through the peat moss and back into the tank. Now is a good time to adjust the flow to make it run smoothly and gently.
Connect your air pump to your air stone using the other tubing, and place the stone in your tank. Attach a sponge filter for added filtration for your fish. Plug the pump in and you should see oxygenating bubbles rising through the water—your system is almost ready.
Check the pH level of your water. It is best somewhere between ph6.8–ph7.2, with ph7.0 being the ideal. If you have to adjust the pH level, now is a good time to do so. If your water is clear from chlorine and chloramine you can add your fish immediately—otherwise, let the water sit for 24 hours or treat it with a water conditioner before you begin.
Since your tank is not yet cycled, you will need to add your fish very slowly, gradually introducing additional fish to the tank while the bacterial colony in your grow bed grows to support them. You may need to perform daily water changes at first, in order to clean the water for your fish before the plants have a chance to do it for you.
If you take good care of your aquaponics system in this period, you should be ready to add plants within 4 weeks when the system is completely established. Introducing them slowly will make sure that you do not upset the careful balance between your fish population and plant population. Leave your actinic light on once you plant the seeds and wait for results to bloom.
Fish selection and care
For your first attempt at an aquaponics setup, avoid selecting fish that are too delicate to survive any water quality issues. Hardy species that can tolerate the varying water conditions that will be present in the beginning are highly recommended. platies, catfish, kribensis, danios, tiger barbs, dwarf gouramis or goldfish can all be used with success.
The notoriously messy nature of the goldfish is actually a benefit in this circumstance, since increased levels of fish waste mean more food for your plants. So long as you do not overwhelm the balance in nutrients between the plants and fish, you will enjoy success.
Plant selection and care
While you can grow just about any plant in an aquaponics system, you will find that fruit-bearing plants and spices may not grow to their full potential from this kind of setup—they will need a more robust, higher maintenance system. With the system described in this article, however, you can grow spinach, lettuce, basil, parsley and many other leafy green herbs.
If you decide to transplant your plants from soil, take very special care to thoroughly wash away all of the dirt surrounding the roots and to clear the plant’s entire surface of insects or other pests. Transplanting is an easy way to introduce an invasive species to your system without knowing it.
Maintaining your aquaponics system
The system described in this article has two major inputs: fish food and electricity. You will want to make sure you do not overfeed your fish—a single feeding should consist of enough food for your fish to consume in 5 minutes and no more. Your tank may also gradually lose water over time to absorption and evaporation, so you should perform a monthly 10–15% water change and refill that keeps it topped up.
Your plants’ mineral needs may need to be considered as well: Flowering plants and vegetables may benefit from having additional minerals added to the water at the start. Also as time goes on, the nutrient export must be replenished. If you notice that your plants are struggling, you may be able to find help in the form of liquid fertilisers designed for aquaponics systems. They contain soil components like phosphorous and potassium that your plants may be missing.
If your plants are growing nicely and your fish are active and healthy, then you’ve done it! Good job on creating your first mini aquaponics system. Cosmetic improvements can be made to the aquaponics system by boxing in the growbed to hide the tubing and wires. Now you can relax and enjoy the fruits of your labours: healthy fish and fresh home grown herb and spices. You can nibble on some lettuce while admiring your fish.
Adjustments to your aquarium aquaponics system
If there is too much fish waste in the system, instead of reducing the fish, add more sponge filtration. If the plants are not growing then try different plants. If the plants are growing long and stringy then they are not getting enough light. Increase the lighting. Keep checking the ph. If it keeps rising then add more peat. If it keeps falling then add some coral sand.
You should experiment with growing different plants. You can also try increasing and decreasing the pump flow rate, thereby increasing or decreasing the water around the plant roots.
If you get bored of your aquaponics system or it is not working out, you can always remove the plastic growbed and have just an ordinary aquarium. Or you can do more research to do it more professionally.