Hi guys and girls i`m just starting out in the hobby and have a few questions. I`ve started to set up a 20g reef, how good does the circulation have to be and is it possible to create too strong a current? I`ve added all the live rock and some corals etc and i`ve recently added 2 common clowns which seem to be struggling against the current. I have 2 power heads at either end of the tank pushing out 5g / min, how should i position them?