I have had my Bio-cube set up for about 2 months now. I just added 2 clowns, and one angel fish in this weekend. One day however, i was missing a clown fish. I later found out that the clown fish had gotten over the back all of the bio-cube and into the filter system. Luckily I was able to save him and he is swimming around fine now. I tried to take some of the water out of the aquarium, because there was about half a centimeter of water flow going from the tank into the filter system. But when I took water out of the main part of the tank, it lowered the level of water in the filter system. And when the filter system did not have enough water, the filter system did not work. So my question is, how do I stop a water flow going into the filter so my fish do not swim over the wall?