I agree with the oscars in 75, but a 125 is SO much better given their max size. True on the eels also, i forgot how big they truly gotI'm going to agree/disagree here. a single Oscar could be alright in a 75 I think, but 2 no way. a fire eel, while extremely flexible is easily capable of 30"+ lengths in aquariums. I wouldn't keep one in less than a 250-300 gallon...I want one for my 310 and that's only 36 inches wide...