crabs

I am currently running a 16 gallon tank with a Fluval C3. I've always wanted an invert tank but have never actually gotten around to setting one up. I was thinking about breeding snails (pond snails, mystery, ramshorn, etc.) as well as cherry shrimp to raise as live food for my fish in the 55...

learning that more than 2 crabs would be ideal, i would like to adopt a few more, but do not want to support petco or petsmart. any ideas?

 100L :  6 glowlight tetras, 6 guppies, 4 red eye tetras, 2 golden balloon rams, 2 penguin tetras and 3 Melanistius Corydoras I have a 100L tank and the Info is above i would like to know if there is a type of fish that will be quite large and elegant looking or crab, shrimp, crayfish or lobster...

I just bought 2 red crabs and bought a Fluval edge to keep them in, I have plenty substrate, and wood for them to climb, nibble on, with part of it above water level for them.   I was just wondering about heat, whats is the best temperature for the crabs to be kept at? and is it even worth me...