In iAVs , the simple way in invariably the best, but we acknowledge that there will be situations – where the biofilters are positioned to drain directly back into the fish tank – is not practicable.
For these situations, we simply incorporate a sump tank into the design.
A timer-operated pump moves the water from the fish tank to the biofilter, which then drains into a sump tank. A float-operated sump pump then raises the water from the sump tank back into the fish tank. This arrangement allows for the use of a relatively small sump tank.
Depending on the circumstances, it may be possible to dispense with the float-operated pump and just put the timer-operated pump into the sump so that when it is triggered, the pump raises water from the sump tank back into the fish tank…displacing the existing water in the tank into the biofilter. This is the more practical way to configure the system if you have a large enough sump tank to ensure that it holds sufficient water to allow for the flooding of the biofilters while waiting for the water to begin to drain back into the sump tank.
The two-pump arrangement will obviously use more energy than the single pump option but, when you consider that either pump will only run for about two hours per day, the added energy cost is hardly an issue.