I just started my setup for 2 red-clawed crabs, i will eventually post a picture when it's decent looking.
Basically, i'm using an eclipse system 3 half filled with water, I removed the stock filter and added a HYDOR pico internal filter.
My substrate is gravel and i have a small lava rock in the middle so they could get some air.
Since the crabs were kept in freshwater i'm increasing the salinity so the are acclimated gradually. Probably gonna get it up to 1.005