I think your set up sounds fine. My only worry would be the shark in the future. I currently keep two sevs in a 75 with one small pleco (will grow to 7 inches only) and five blackskirt tetras (and one raspora I can't catch!). I have an AC 110 and an Eheim 2215 and a large sponge filter running on it and don't have any issues with the bio-load so far. My Sevs were apparently wild caught so the aggression level is higher than domestic sevs I think. I may have to rehome the smaller sev eventually. Currently they are 4 and 3 inches, and starting to grow up nicely (began at 2 and 1.5 inches a few months ago). The larger one sometimes beats on the the little one, but she(?) also fights back and is more of the aggressive eater. Interesting tank dynamic anyway. I am monitoring them closely and may rehome her or put her in a spare tank. They don't bother the schooling fish or pleco. They seem to be conspecific aggressors. I had a third sev in their initially which is now in a 125 with an oscar three times his size and he holds his own just fine. He use to terrorize the other two even when tiny. I have learned to think of Sevs as selectively aggressive, in any case, and not the peaceful fish they are often said to be.
BTW, I am the guy that got Jaw's Obic. A cool fish indeed.
