i keep australian redclaw crays (cherax quad) with a variety of your small standard fish such as fighters, tiger barbs, zebra danios, black widdows and platys and they have never bothered them. I believe this is because of the amount of bogwood and caves for the crays to hide in aswell as the size of tank for the amount of fish kept in there. i also use floating plants like guppygrass/watercress for the fis themselves to hide in which helps if youre keeping smaller varieties of fish. I would also suggest that larger peaceful fish that are reasonably quick and do not have long flowing fins are also compatible with crayfish and they tend not to bother each other. i hope this info helps you make a decision. cheers.