This is really good info, but red claw crabs aren't freshwater crabs. They are brackish water crabs. I just recently found this out after doing some research online
Most of the info we find online isn't very reliable either. I used to have a red claw (from Petsmart). Had him in a little one gallon tank (temporarily) which was way too small. Either I didn't watch the water conditions well enough or my tap water had a chlorine spike.. I don't know. After about 2 months, he just stopped eating and died a short while later. Since then, I got a Rainbow Crab at a better LFS and he's doing great. The lady at Petsmart was quite knowledgeable about freshwater/land crabs in general, telling me about how she floated a chunk of styrofoam in her tank for the crab and made sure he had a way of climbing up there. Not very attractive, but it was a great suggestion. That gave me the idea to use floating cork bark the same way... which would look more natural. That's easily found in the reptile/terrarium section - totally natural product, so no added chemical stuff to worry about. As for feeding, the LFS place told me they fed their crabs a small chunk of krill once every 3 days. After looking at their price ($10) for a pound of frozen krill, I realized it would be cheaper to feed him real fish or even shrimp from the grocery store when that's on sale. Or even check out what I could find at a local bait shop to keep in my freezer. My Rainbow Crab also gets bloodworms and shrimp pellets. I basically go with a lot of variety for him. He's about 5 inches across now and he seems to get hungry every other day. I've yet to find anything of very much use online about feeding them. But we do know they need a good amount of calcium to maintain that exoskeleton.. and a good amount of protein for inside growth. Just that too much of good thing might make him outgrow the exo too fast. They also really like mango and papaya. So try giving him a small amount of two things at the same time, so you can see which he chooses. And don't lean too heavily either way between fruits/veggies and fish/meats.
Edit: When my crab molts, it usually takes him about 4 days before he gets around to eating the exo he left.