Crack in Tank! Advice Needed!

[Olraz]

Hey everyone!
I am currently in the process of building a vivarium for hermit crabs, or as we know, a crabitat. It will be filled with eight to ten inches of substrate. I just got this 46 G tank from a neighbor and was excited to begin however I just noticed this crack in the back side of the tank. It is a quarter way you from the bottom. Can I fix this or is it safe to use? It did not leak when filled with water during the cleaning

 

[Blueberries]

I fixed my cracked aquarium tank with 100% silicone - it is sold at most petstores and even the hardware store. You have to let it air out for a while tho before you can safely put water and fish in it. I assume if it’s safe for fish it would be safe for a hermit crab?