I had a canister filter on my 55 gallon before i knew better. lets just say disaster!!! I even took out all the bio balls when my nitrates spiked and replaced it with live rock bits, but this must have made to much pressure on the filter and it started leaking and no matter how i tried to alter it for the live rock it just would not work.
I agree with everyone else, go with more water changes, protein skimmer and even add some more rock if you can for filtration stay away from canister filters your wasting your money.