As for your filtration, I would go with dual filters (also dual heaters), one on each end of the tank, rather than a single filter. It helps circulate the water better and if my chance one happens to have a problem, you still have some filtration. Also, with the extra messy oscars, you need extra filtration. I am running 2 Fluval 304s on my 75 gallon and they are great. I would definitely recommend them. I also mentioned heaters. I am also running Hydor Inline heaters with the Fluvals. Those are a little more expensive but work great. It's also something else that is out of the tank so you don't have to look at the heater sticking on the back glass.