Now my issue with your tank is Imalizard is that your sand seems a bit too damp for hermit crabs and I also belive that you tank seems very bare! Do you have any other fish tank ornaments which you can use to make your tank more interesting for your hermit crabs!
Sorry if i seem rude! I have kept hermit crabs for about 7 years now, I started out not knowing mcuh about them but after many years of research i have found that a tank that provides your crabs with pleny of areas to climb and hide keep them much more content with thier enviroment. In the wild crabs are known to walk upto 5 kms in a night. I always ensure the tank is spot cleaned every day, and I rearrange the arnaments and clean the ornaments every week.
I will post a picture of my tanks soon to give you an idea of my tanks.
Now I am also admin on several hermit crab forums so if you have any questions i am happy to help out with your queries.
Cheers
Sam