Are you using the Biocube filtration? and did you find the flow of water
Yes I am... I had to MOD the first chamber in order to get more flow.... there is a problem with the Cubes in that the first chamber wall hieght before the water enters the ball chamber is too high.... with cutting out a section you get more flow which lessens the chance of back flow from the tank.... but it does pump the water fast..... if you difuse the out flow it is ok but it does tend to move move sand around a bit so position is the key.....here is some mods i did-
lowered wall from chamber 1 into 2
new pump to increase over all water change
carbon insert, i use 3 just placed over the bio balls... found that once the brown bio filtration stuff decreased the flow into chamber 2
if it was a Salt tank people were removing the bio-balls and the wall from chamber 1 into 2 completly and using coral substrate....
if i was to do it again i would not get a Bio cube... but would set up a system with different parts.... but it had been 10 years since I had a tank and well wanted a easy start... the next tank is going to be a 75 gallon set up... have not figured out the specs yet but with this forums help I know I will not have a problem picking the right equipment....
hope that helps