I agree with Sandtiger!!!! Although it would take the focus off the oscars fighting I definately dont recomend putting a jag with them nor a Devil! That would be devistation within your 75G tank. Big train OBVIOUSLY didnt know what he was talking about or was just a total jerk and didnt let you know that he was J/K. Anyways all in all your best bet is getting at aleast a 150 gallon tank or bigger and if you want to add more fish! You can have an amazing show tank or centerpiece if you would be able to invest just a little bit of money into something that all your friends and famialy would drop their jaw at. I have spent a couple of thousand dollars between all my tanks, maintence, food, plants, filteration, fish, medicine, aquascape, And I only have 6 tanks. All in all My 150 gallon tank cost me $500. That included me getting the 150G tank, all oak canopy, base/ cabinets,
lights, fluval 304 canister filter, 100lbs of gravel, and renting a commercial van from Enterprise for the day to drive 150 miles to get it. If I bought this from the pet store it would have cost me at least $1,200- $1500 to say the least!. I found my tank looking through every online classified add within 250 miles. I just happen to get lucky, and their are allways buys like this all the time. People get bored with the hobby or get married and the old lady doesnt get into monster fish so the lonely guy has to loose his prize possesion for the sake of his petty little merriage that will only end up being 8 months long. Or something along that line! Im so serious just listen to my advice and you will be glad that you did. Best of luck!