I am bad 12-15X tank volume per DAY I am sorry about that. Fishman you are right thanks for calling me on that.
I try for 10x per hour. IMO a 55 is too small for an adult Oscar and needs a 75. On my 100gallon (with an Oscar) I run a wet/dry at 1000gph. Allowing for return length and bends puts it more towards 8-900gph as the pump is a 950gph and secondary is 280gph. On my 90 with Oscar, I run 2 Emperor 400's