do not put anything larger than 2 oscars in a 75, and only if you have the tank really over-filtrated.
i've got a 300 with a super red arrowana, 1 silver arrowana, jardini, 1 red dragon flowerhorn, clown knife, 1 jaguar, 2 turquoise severums and 3 oscars. my tank flows about 4500gph.
everyone...