Yes because moon sand has many chemicles in it that are not yet introuduced to the crab. Something may happen to the hermit crab so it would be safe not to put the hermit crab in the moon sand, since scientist have not experimented it and found out for sure.
I think that the fish rock might be a little too hard for your hermit crab because he needs soft enough sand to be able to molt and when they molt their skin is sensitive so the fish rock will probably make him uncomfortable.
it depends how big the hermit crab is or the fish bowl
The depth of substrate in a hermit crab habitat should be deep enough that it covers your largest crab at least by 3x. It should be made using about 5 parts playsand and 1 part coconut fiber, moistened to a sand-castle making consistency.
Yes, you could possibly drown it. Hermit crabs can only swim in an inch of water. That is unless your hermit crab is huge, it could go in 2 inches. I WOULDN'T RISK IT.
if your hermit crab pinches you put it under cold water
no, hermit crabs live at the beach so it is not part of their natural environment. I suggest putting sand or coconut fiber in the bottom of the cage.
It depends on the hermit crab but I would personally say just to be careful No the big one might hurt or bully the smaller crab.
No. Hermit Crabs need a substrate that will allow them to bury themselves. They cannot bury themselves in gravel. I suggest sand, but it can get messy and attract sand fleas. A ggod idea is to look for substrates out here that are "hermit crab friendly". There are several and a great brand is "T-Rex" or "ReptileSupply.com" since most reptile supply companies also make products for Hermit Crabs because they need similar habitats.
Sand or rocks are best.But, many crabs like coconut fiber. you can find it at most pet stores.
down the toiliot
You should let it mold. It is part of life for a Hermit crab.