Get as much info as you can on the different species. Coomon wild craws here need water in the 60's. Blue lobster need a much higher temp. Bumble bee's need another and so on. Also, live plants will help with their diet but won't last too long, veggies once in a while will help them also. Just like anyhting else, keep their diets varied as much as possible and make sure it is clean. Unlike their wild counterparts, captive bred ones don't have the immunities.
Best of luck, I think they are really cool and if I ever have room will have a few of my own.