Have you got any species in mind Sven? Some such as the Arc-eye Hawk can get quite big and become pretty aggressive as they age, and with out something like Ken's 10 footer there's no way you'd get a pair to live happily unless there already a mated pair.. I read somewhere that Hawkfish are monogomous (I think thats the word anyway :confused:) meaning that once paired and one of them dies they will rearely take to another partner... Some others such as the Pixie have been found in groups of several individuals with a dominant pair... As said above most all are easily kept, and take prepaired foods surprisingly quickly after being introduced... If you stick to the smaller species (Flame, Pixie, Dwarf, Longnose etc) you shouldn't have a problem with medium to large CBS.. As Shane said they are usually best of kept singly, tho you can keep different species together, best ones for this are flame and pixie or dwarf.