I just got a group of 5 multis. 4 of them have taken to the shells and the fifth has decided to take up residence in a vertical crack between two rocks. I have a 55 gallon tank with a fluval 306 canister filter with the intake on one side and the output of the other angling out across the tank. How much water flow should I set the canister filter to. Should I just leave it running at highest flow rate?