while researching them prior to owning one, I noticed there were so many different verdicts an opinions, which are all respectable, as fish care is very diverse, but in my experience, no, dwarf crawfish cannot be housed with fish. I tried to keep one in my community fish tank. when I first purchased her, she was missing a claw and was fairly small. once she got bigger and grew back her claw in a shed, all **** broke loose. she grabbed 4 guppies by the tail, attempting to drag them into a cave and eat them, like something out of a horror movie. she didn't do this out of hunger; she was well fed. I caught her in the act the fourth time around and moved her into a separate tank. what was surprising, was these guppies weren't small; they were full-grown. 3 of the guppies were fantail, which I suppose made it easier, but even my round tail wasn't safe. he did, however, heal faster since his tail sustained less damage. she even terrorized my gourami and attempted once to take a chunk of his tail. the only tankmate she didn't terrorize was the Amano shrimp because they were equal to her in size and much faster. upon relocation, a placed her with a short-finned female crown tail betta (they are notorious for latching onto long betta fins and feasting as the fish swims), who had been housed with dwarf crawfish in the pet store. I caught the dwarf attempting to sneak up on her and attack, but the female betta had experience with them in her pet store tank, so she was very good at keeping her distance. about a month later, I put the betta in a community tank. it was larger, so she was happier there. could the dwarf crawfish+ short-finned betta duo workout long-term? perhaps, but the number of times I found my dwarf crawfish wanting and actively trying to eat her was unsettling. if the betta has started to slow down due to old age, which is inevitable after a couple years, she may simply become an easy target. so in my opinion, no, dwarf crawfish should NOT be housed with fish or small shrimp. and if you do decide to, expect a fish may turn up dead, or with their fins completely torn. they simply have a remarkable grip and are extremely strong.