i usually think of silver dollars as being dither fish or a nice school to add to a tank of other big fish - as long as they are big enough the can do with just about anything - i have two almost full grown common silvers in my cichlid tank with a pair of jags, oscar, firemouth, and a blue zebra mbunda (all which are pretty much full size except the jags and oscar that are around 12-13in) none of the fish ever both the silver dollars - and ive had those two in a number of tanks with a variety of fish -- they really are a great fish especially if you have a large tank were you can get a nice school of like 5-7