Hello Sustainable growers! In this video we will talk about Aquaponics sump tank. An aquaponics setup is composed of minimum 4 parts which are the fish tank, the growbed, the pump and a flushing system such as the bell siphon. Today we will see that we can add another “buffer” tank to the system and we call this third tank the sump tank. The sump tank can be used for different reasons but generally it allows to main things:

First it allows you to work with a constant water level fish tank which can be very handy if you design an ornamental Aquaponics setup exposed to the public.

Secondly it allows you to position your fish tank and your growbed at any level. In classic backyard growbed aquaponics we simply position the growbed on top of the fish tank and the water goes by gravity from the growbed to the fish tank. When we use a sump tank we position our sump tank at the lowest point and the fish tank can be above or at the same level as the growbed.

Another interesting point is that we will place the technical equipment such as the sump pump into the sump tank therefore we don’t disturb the fish when we clean the pump and we can use this tank to add minerals or other elements such as chelated iron into the water.

Depending where your sump tank is situated, an important thing to have into the sump tank is an overflow (especially if it’s an indoor aquaponics system such as in this video). You simply want to make sure that any excess water will not drop on the floor but goes directly into the evacuation pipe (generally 5cm below the top of the sump tank). When it comes to sump tank size I like to take some security and to work with a sump tank that is approximately 1.5 times the size of the growbed. The reason is that you want your sump tank to be able to hold all the volume of water that will be flushed from your growbed at once when the bell siphon flushes. On top of it you want to make sure that when the growbed is full of water and therefore the sump tank water level at his lowest point, you still have enough water into your sump tank to allow the sump pump to stay completely underwater and to not suck air.

The sump pump size remain the same as in a classic aquaponics system without sump tank excepted that you need to make sure that the sump pump is powerful enough to raise the water at an appropriate water flow up to the high point of the system (generally the fish tank).

You can also add a sump filter into your sump tank mechanical filtration and biological filtration are very welcome into your sump tank. It is generally very easy to add few moss layers into the tank in order to stop any bug particle to come in contact with the sump pump and therefore you extend the sump water pump life.

The position of the sump tank is generally the lowest of the system and one option is to put it into the ground, in this case the water temperature variation will be limited. If you take this option think of a water evacuation otherwise you will have to use the sump pump the day when you want to empty the tank.