I'd upgrade to a canister. IMHO hang on back are more suitable as back up filters or for smaller tanks due to their lower biological efficiency.
The only issues I see is the dragon goby and if the catfish is a colombian shark they'd both require brackish conditions.
The other issue being the Lep who may or may not be a problem due to their habit of nipping. At 12 inches he should be fine in a 75 but there may not be enough room for anything he picks on to run.
The only issues I see is the dragon goby and if the catfish is a colombian shark they'd both require brackish conditions.
The other issue being the Lep who may or may not be a problem due to their habit of nipping. At 12 inches he should be fine in a 75 but there may not be enough room for anything he picks on to run.
