We have our RES in an 85 gallon tank that we keep about 1/3 full (probably about 25-30 gallons, or about 7-8 in water height in a 21 in tall tank). we have been using an in-tank fluval filter but it just isn't cutting it and we are trying to find something to cut down on water change frequency.
went to upgrade to a canister filter, bought a fluval 306 rated for 70 gallons. there were a couple of problems 1) the manufacturers instructions state that the water level can be no more than 7 inches below the top of tank (i am not expert in filtration, but am guessing that the filter isn't powerful enough to pull water from a lower level than that) and 2) the intake apparatus that comes with the filter was so long that it was not possible to meet the manufacture depth requirements without filling the tank to the top (i.e. the bottom of the intake had to be at least 3 inches above the bottom of the tank, while at the same time, the top of the intake where it is connected to the tubing had to be at least 3 inches below water level, to be honest, i could barely meet those requirements with my tank completely full!!!).
any ideas on a canister filter that can handle low water levels like this?
thanks in advance for the help.


