I'm a new fish keeper, so forgive me if this is a silly question. All I've ever kept in the past was bettas and frogs. We recently bought a 100gal set up and have 1 baby Oscar (4in long). We tried putting a common pleco of about the same size in the tank and the Oscar harrassed the pleco who eventually died. I love plecos and I'd really like to have one. What size/type would be best? I'm also considering a 2nd Oscar for the tank. Is that going to overwhelm a tank of that size?