I just posted most of this in a thread over in the Reptiles and Amphibians section where someone had started a thread: http://www.plantedtank.net/forums/sh....php?p=2082613
The crabs are very easy to care for and breed well once old enough and established.
I keep both of my groups (2.2) in Fluval Ebi tanks. I use the fluval stratum substrate, and I layer several small pieces of ghostwood on the bottom to set up little nooks and crannies for the crabs to hide. The substrate stays wet - and I have cleared substrate away towards the front and set up a little pool area. Then in the rest of the tank, I have ghostwood branches covered in moss and miniature orchids (Pleurothallids primarily). While the branches are more the benefit of increased space for planting - the crabs will climb all over them (and sometimes knock the orchids over if not yet well rooted).
Room temps - no additional heating. I did find that in my office viv - before the heat in the building was turned on - the crabs were much less active when temps got in the mid-low 60s. They are most active in the evenings, but also in the morning.
For feeding, I offer a mix of HBH hermit crab food and Tetra hermit crab pellets (crushed) to which I add additional calcium carbonate and also some astaxanthin to help with color (and I find it makes a big difference). Many of the hermit crab foods out there have low calcium if you look at the ingredients, so make sure to add a little more (I added a couple of tsp to a 2.25 oz container). I crush the pellets between my fingers - as the crabs seem less likely to eat them when they are whole - even if soft - and they tend to mold quickly. I don't feed live food currently. When I had a ready supply of FFs, I would also feed dusted FFs - but they seem to do fine without them.
As for breeding, they do it all on their own. One day you will see little tiny crabs running around. They are tiny when they leave the female, with carapace lengths of 1-2mm. I let them grow in the tank until they get about 4-6mm carapace length - and then pull them. There have been some reports of adults feeding on babies. The babies tend to hide in the water and under wood and rocks at the waters edge - so I think with enough hiding space, they can safely coexist. But when they start getting bigger - I worry about stress on the babies and adultes.
With my two female Red Devils, I pull about 40 baby crabs or so out every 6 months. My mandarin crabs seem to be slower breeders, but I haven't had them as long.
Here is a poor pic of one of my tanks.