The design and function of aquaponics are similar to hydroponics.
Both systems use water to deliver nutrients and do not use soil to grow.
With hydroponics, you must change the water often causing many gardeners to ask – Do I need to change the water in aquaponics?
The main difference is that aquaponics uses fish as a nutrient base, which also contributes to monitoring and topping of the water to ensure good water quality for your fish to avoid pathogen build-up, which could kill them.
If your aquaponics system is set up correctly, you should not change the water unless you have over stocked the fish.
The water level will decrease due to evaporation and you will need to top-up the water, which will also help reduce bad bacteria.
A good aquaponics system should be good at self-cleaning and should require very little in the way of water changes.
How Does Aquaponics Work?
Aquaponics is designed to mimic natural waterways and is a great way of producing crops in a small area.
They are very sustainable.
The major input for an aquaponic system is fish food. The fish eat the food, and it results in waste.
The majority of this waste is ammonia that the fish secrete from their urine and through their gills.
The rest of the waste goes through a process called mineralization.
During this process, heterotrophic bacteria eat the waste, uneaten food, and decaying plant matter and create more ammonia and other compounds for fish and plant life.
As long as ammonia levels remain below a certain threshold, it does keep the fish and plant life fine, but if levels begin to climb too high, it will become toxic to the fish and the plants.
So this is where nitrifying bacteria can help. This bacteria, which is naturally in soil, air, and water, will convert the ammonia into nitrites and then into nitrates. This is a healthy source of nutrients for the plant wall.
Both types of bacteria will cling to the walls of your tank, on the growing media, on organic matter, and even under rafts in your system.
These bacteria that supply ammonia and nitrites are natural and will be present all the time in your system when there is ammonia and nitrites.
A healthy aquaponic system depends on keeping these three components alive and thriving:
- Fish, plants, and beneficial bacteria.
- These three depend on each other for survival and all needs to be incorporated into a system where all needs are met.
The Process: Bacteria consume the fish waste, which keeps the water clean to the fish and gives the plant the nutrients it needs to grow. The plants grow with the nutrients, and in turn, they filter the water keeping it clean for the fish.
Should You Change Water in An Aquaponics System?
As previously stated, water should remain unchanged in an aquaponics system that functions effectively.
In addition, when first introducing fish into your set up, you want to give your fish time to cycle to establish the right ecosystem.
However, if you see that you have an algae issue, you are going to want to change the water. Algae is a pest and can lead to many issues.
Two concerns that algae can affect by introducing problems are:
- Nutrients for plants
- pH of your aquaponics systems
However, before you even get started, I’m going to provide you solutions to prevent algae from growing, to eliminate having to change the water of your system.
Shading
This is the easiest and fastest way to cut back the growing algae in your system.
Green algae will grow and reproduce because it needs light. So, you can shade your tanks or cover them with black plastic or a tarp.
Many growers will paint a sump tank and transparent plastic black and they’ll put white on top. This will reflect the sunlight and keep the water temperature down.
It Works: If you have algae issues on your media beds, you can shade by adding more gravel/rock, so that light does not strike the moist area.
Filtration
Mechanical filtration can affect algae removal.
When it comes to filtration devices, they can get costly, but you can easily build them. Just use filters, screens, and centrifugal settlement devices to scoop the algae out.
A grow bed operates as a mechanical filter and strains the algae out of the water.
Alternatives
Some growers apply humic acid as a preventative measure against algae growth.
In deeper tanks, if you put this in, it will darken the water preventing algae from growing since algae requires light to grow and reproduce.
Furthermore, adding humic acid to your water will chelate the plant nutrients thus benefitting your plants as well.
Why Water Doesn’t Need to Be Changed
In addition to ensuring the pipes and pumps in your system are operating correctly and squeaky clean, there really is not a lot else you have to do for the water in your aquaponics system, except for monitoring the pH.
This is because an aquaponics system is an eco-system, not just a system.
There are three zones in your aquaponics system:
- Surface
- Root
- Mineralization
Zone 1: Surface
This is the top 2” of the surface, and it serves 2 functions:
- It prevents moisture from evaporating because it creates a dry zone.
- Dry pea gravel here helps reduce collar rot in your crops and reduces the chance of powdery mildews and algae forming.
Zone 2: Root
This is the moment when the magic happens.
The root zone is 6″ to 8″ deep. Once the bed is flooded and it drains, the oxygen moving to the roots of your plants maximum. The action is between beneficial bacteria, the beneficial microorganisms, and worms.
The flood cycle is the mechanism that distributes the waste particles across the grow bed. The worms break down the solid matter, and then release minerals into the worm tea.
When the beds flood again, the worm tea gets distributed to the plants root zone.
Zone 3: Mineralization
The bottom two to three inches is worm castings plus fish waste solids, down to about 40% volume since entering the system.
During the flood and drain cycle, this zone will be refreshed with oxygenated water.
Conclusion
Simply put, the answer is no, once your aquaponics system is running, you will never need to change the water.
However, while your aquaponics system is certainly contained, there are still some maintenance aspects you will need to be mindful of in order for it to perform efficiently.
When you are filtering things out with systems, and doing everything else you need, water logging with blocked pumps and pipes can happen.