I have a 75 gallon tank too! I have never kept crabs before but I have kept crawfish and they did well in the tank with the fish! I kept angelfish and some South American Cichlids with them. If you need some ideas, I currently have an angel, a festivum cichlid, 2 gouramis, a severum, a rainbow cichlid and a school of rainbowfish. They all get along just fine ime.
Brice131, from what I've heard crabs when they molt get really vulnerable and they'll be attacked by larger fish. So with crabs I'd probably say angels. Also crabs need dry land I think...maybe check on that.
Wait, Angel101, you kept crayfish with SA cichlids? How did that work? What kind of cichlids were they? I have looked on a bunch of different websites and stuff and everyone says the crayfish will pick off the cichlids until it molts at which point the cichlids will hunt it down and kill it.
*livebearers, not angels. Angels will attack crabs.
But the crayfish thing annoys me because I have SA cichlids and I really, really want a crayfish, but I don't want it killing everything in the tank.
Yes, I kept a crayfish/crawfish with my SA cichlids. unfortunately, the crawfish did pass a while ago due to an illness, but I kept it with a severum that I got when it was a juvenile and an angelfish as well as ram cichlids. my fish and crayfish never really bothered each other and coexisted nicely because I started them as juveniles. like the severum which is now probably close to 10 inches was maybe 2-3 inches when I got it. the angels and rams were around the same size too. I guess it does depend on the fish too but just in my experience I never had a problem.