Molting is one of the hermit crab’s unique characteristics and behaviour traits as this activity frequently occurs every few years as your hermit crab continues to grow and outgrow its shell. Because it requires new skin to grow, it has to hide away. Preferrably inside another larger shell.
Therefore, there must be an abundance of shells and leaf litter scattered among the marine plants, tree branches, rocks, pebbles, stones, six inch bottom sand substrate in your tank. Because hermit crabs are susceptible to harm and damage while molting, they instinctively hibernate during the molting process.