HCA: Hermit Crab Association

I have a marine tank, I do believe its being caused by food, but it doesnt seem like its algae, is algae normally white in marine tanks?

Is there a way to stop a marine tank from growing mold? Is the mold safe for the crabs? I have white mold that keeps growing. I tried scooping it out and it grew right back, is there anything I can do?

He is currently in salt water yes but its not very deep as I wasnt sure if he was marine or land and didnt want him to drown and wanted him to be able to crawl back out if needed. Hes been hiding in the water for the past 7 hours though so Im assuming marine? Should I go ahead and fill the tank up w...

I got some nerite snails in the mail and one turned out to be a crab. I don’t know if hes a marine crab or a land crab. He has dark red legs which made me think he was a land crab but when I put him next to water he crawled in and has be in it over an hour. He’s the size of a large pee so it’s hard ...