This is a good start, but I’m afraid you need to do a little more to it. Hermit crabs are tropical creatures and require salt and fresh water. From what I can see, your tank lacks a saltwater dish. When making water dishes, they should be deep enough for your largest crab to fully submerge in. Drowning isn’t much of a problem with hermit crabs, for they can be submerged for close to an hour thanks to their modified gills. Always make sure you have an easy way for the crabs to easily get out, for they need to exit the pool at some point or another. Another thing I see is that you are using all coconut fiber. Coconut fiber is made to be used with animals less sensitive than hermit crabs. The reason being is because they add acids to the fiber to work as a catalyst to break down mold and uneaten food. Although this seems like a good idea, it isn’t when it comes to hermit crabs. This is because hermit crabs spend a large amount of time molting. Molting is the process of shedding the exoskeleton and growing a new one. Crabs will sometimes spend months under the substrate molting. The CSJ has some great articles on this. Back to the main point, when a crab molts, its bare, unprotected, body is exposed without an exoskeleton. During this period, the exosksleton is not present to protect a crab from the acidic environment under the substrate. This long period of exposure has a negative effect on the crab, for the acid eats away at the crab’s bare skin and cause molting deformities. This is extremely harmful to the crab and can cause surface molts and sometimes kill the crab. The best way to avoid this is to simulate a crab’s natural environment by mixing NATURAL sandbox sand and coconut fiber in a 5:1 ratio.The sand can be bought at a hardware store and is often called “Play Sand”. DON’T buy “Calci-Sand”, “Calcium Sand”, or “Repti-Sand”. It is important to note that that you must have at least 6′ of substrate in your tank to allow for proper molting.