An amphilophus sp. red isletas is a nice choice. I just got a little male at 6" from a local breeder and love the personality on him. Trying to replace an Oscar will be difficult but you pretty much cant go wrong with most from the amp. family.
I sold my salvini a few months back and am regretting it big time, will be getting another one at some point in the future. IMO, even tougher than convicts pound for pound... would look good in your 75, here's the female I stupidly sold.....
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