In flood and drain aquaponics, one part of the maintenance consist of cleaning the grow-bed. Let’s see why and how to clean and maintain the aquaponics grow-bed.
Why should we clean clean the aquaponics grow-bed?
When you start aquaponics there is generally a 6 month period of time where the ecosystem is building up. After this period, the bacteria and other fungus reach a good diversity and density. Therefore, the nutrients are highly available for the plants and the productivity is very high. Even after this point, the grow-bed is continuously building up with organic matters. This accumulation is composed of different particles: dead roots, fish poo, bacteria bio-film. Unfortunately, with time those particles can clog the media. They form a dense and compact “Cake” almost waterproof. This phenomenon will cause the following issues:
Nitrate increase
Let’s assume that your system is well designed and you respect the maximum fish biomass capacity of your system. Therefore, the quantity of bacteria is enough to transform the ammonia in nitrite and the nitrite in nitrate. However, the large quantity of nitrate released into the water is sometimes higher than the plant needs. As a result, the nitrate concentration will continuously increase into your water. Consequently, you will have to regularly renew the water to keep nitrate down. Cleaning the grow-bed and reducing the quantity of organic matters will significantly decrease the quantity of nitrate produced. As a result, it will decrease the quantity of water change necessary.
Poor water flow
In aquaponics, the whole ecosystem is relying on the capacity of the bacteria to transform the fish poo into plants fertilizer. Also, those specific bacteria are what we call “aerobic”. Which means that they need oxygen to live. If the grow-bed media is clogged with organic matters, the water can’t circulate properly. Therefore, some area of the grow-bed will turn “anaerobic” which means without oxygen. This situation can be detected if you see some constant water pools near your water inlet. If nothing is done, the good “aerobic” bacteria will die. Furthermore, they will leave the room to other anaerobic bacteria responsible for fermentation. The setup will then smell very bad and the ammonia level increase until the fish die.
Rotten roots
If the system is clogged by organic matters, the media will become sealed. As a result, the plants roots will not be able to breathe properly. In this case you will see the plants growth slowing down until a point where the plants will die. In order to avoid this problem we must clean the grow-bed before the media becomes clogged.
How to detect a clogged media
When you dig into your grow-bed, the media should fall down as if you are digging into a sand bed. Each particle of the grow-bed must be independent and not clogged to others. If you see a “cake texture” when you dig into the grow-bed, this is a sign of clogging.
When is a good time for aquaponics grow-bed maintenance.
It is generally easy to see a grow-bed media starting to clog. However, the best time of the year to clean a media grow-bed is winter. For the reason that you avoid to disturb your plants during their best growth time.
How to clean and apply the aquaponics grow-bed maintenance
Plan
In order to clean the grow-bed, it is important to plan the operation. Indeed, you must not feed your fish the day before and during the whole process.
Prepare the grow-bed
The D day, turn the water pump off. Then, we want to avoid the “dirty water” to fall back into the fish tank. Hence, plug a pipe at the end of your bell siphon going directly into your classic garden or to a bucket. Because we will remove a large quantity of organic matters, we will use it as a fertilizer in our classic garden. If your garden is mulched, you can push the mulch away. You will cover it back at the end of the process. So the “mud” will not be visible.
Remove the plants
The second step is to remove all your plants one by one. Place them in a safe place in a shady area. Be careful, the roots must not remain exposed to the sun.
Agitate your media
The third step is to move the media in order to release the organic matters trapped between the rocks. Then, you will add a water pipe in your grow-bed and turn the tap on. From there, there are different techniques and options depending on the equipment you have available:
Air blowing
If you have an air compressor or strong air pump you can use it too. Fill the grow-bed with water. Then, blow air in the media in order to move all the media particles. It will release the organic matters trapped in between. as a result, it will clean the aquaponics grow-bed.
Air + water
You can associate your air hose with the water hose (tape them together). It will be the best tool for cleaning large grow-beds.
Shovel
If you don’t have a compressor, you can simply use a shovel. Move the media to mechanically dissociate all particles. Before, I strongly recommend to remove 30% of the media in buckets on the side. As a result, it will create some space in the grow-bed. That will help you to move the media easily.
When you operate this step you can remove the bell of the bell siphon. Leave the water over flow through the stand-up pipe. The water going into your garden will be completely black. In other words, full of nutrients for your plants.
Once the all media particles are free, you can continue moving them with full running water. Continue until the water turns from black to brown. The longer you clean the grow-bed and the clearer the water going out will be.
Don’t expect to see completely clear water going out or you will lose too much water. The idea here is to remove 80% of the particles, not to remove everything.
Once done you can put all the media back in place and replant the plants in the cleaned grow-bed. Then, you can put the bell siphon back in place and flush the whole grow-bed. Once done, you can unplug the pipe going to the garden from the bell siphon evacuation.
Now you can turn the water pump on and the system is running as normal. However, please check the quality of the water going back to the fish tank. It will be slightly brown but shouldn’t be black.
After few hours test the water parameters. They may be high. If so, renew part of the water. Keep an eye on your fish and make sure the fish tank is well aerated. After few hours the water should start to clear again.
Congratulations! Your grow-bed is clean and your system ready to go for few more years before the next aquaponics grow-bed maintenance 🙂
I hope the above instructions are clear. To make sure you understand the whole process, I summarized the above in a 12 steps process. I also joined a video below:
The 12 Steps of aquaponics grow-bed maintenance
In the video you can see the clogged media is forming a kind of cake where water can’t circulate freely. As a result of stagnant water, the oxygen concentration will drop and the beneficial bacteria will die. So here are the 12 steps:
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Don’t feed your fish before the aquaponics grow-bed maintenance
Cleaning the aquaponics grow-bed will release a number of organic matters and some of them will inevitably finish into the fish tank. Once agitated those particles will react and may release some molecules. This will affect the water parameters such as ammonia, nitrite and nitrate. The fish will therefore be stressed and if you have been following my channel for a while you know that we never feed fish that will be stressed (see the video there: https://youtu.be/vFeqzrORV_8)
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Turn the water pump off and disconnect the pipe from the grow-bed to the fish tank
We want to avoid the “charged water” to be drained into the fish tank. During the cleaning process, the fish tank will be isolated and the water pump off. The air pump will be on and as we didn’t feed the fish, the water parameters are good and allow us to keep the fish in good condition for hours into the same water without filtration.
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Connect a pipe from the grow-bed evacuation going to the classic garden
We will collect the organic matters and use them as a natural fertilizer for our classic garden. This will boost the production J
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Carefully remove all plants one by one and place them in a safe shady area
Now we can start to collect the plants away from the grow-bed. Note that the plants roots must be managed very gently and not be placed under direct sun exposition. Keep them in a safe (away from birds) shady and moist area.
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Collect 1/10th to 1/4 of the media in a container
We now need to make some room into our grow-bed in order to be able to move the media around. To do that we will remove 1/10th to 1/4 of the media and place it into a container/bucket or other.
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Clean the media in the grow-bed thanks to a shovel and a water hose (be very careful to not touch the grow-bed liner with the shovel)
Now it’s time to actually clean the media. Here we will use a shovel and a water pipe. The aim is to release all the organic matters trapped between the media particles. We want to obtain a fluid media and release all particles into the water going out into the classic garden.
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Clean the media into the container
The media placed into the container must also be cleaned. Place it under a water hose and agitate the media generically to release most of the clogged particles.
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Put the media back into the system
Once the media is clean you can put it back into the cleaned grow bed.
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Put the plants back into the system
The plants can now be planted back in place. Think of the positioning and light exposition. For a better productivity it’s better to place the large plants at the back and to separate the same species as much as possible to slow down the possible pest growth.
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Run some water through the grow-bed until the water flushing away is clearer
Before plugging the system to its original configuration we must drain the last organic matters away from the grow bed. Allow the water hose to come into the grow-bed and allow the water to run through the grow-bed and to the garden. Do it for a while until you see the water coming out of the grow-bed becoming clearer. You don’t have to wait until the water is completely transparent but you don’t want the water to be completely black neither.
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Unplug the water pipe going to the garden from the grow-bed exit and plug the original pipe going into the fish tank
The grow-bed is now cleaned. We can unplug the water pipe going to the garden from the grow bed exit and plug the original pipe going into the fish tank. The aquaponics system is now in its original configuration.
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Turn the water pump on, observe the fish behavior, check water parameters, check water color.
We turn the water pump on. The water from the fish tank is now coming into the grow-bed. The grow-bed water level raise up and flushes back into the fish tank. The fish tank water will turn murky. You can check the water parameters but what is important is to check the fish behavior. If everything goes well you should not be able to see them. If you see the fish at the surface, it’s time to renew some water and to apply the points detailed into this video:
You know now the most important part of aquaponics grow-bed maintenance. It will allow you to produce food all year round.
You will probably be interested to discover my six steps to build and manage an Aquaponics system. Click here to access for free! Thanks and good reading 🙂
