I read you can douse mangroves but i here its a lot of upkeep. I suggest just going with what us had and put the crab in the main display tank, he'll eat algae again she. He realizes he has to and the pods that get into the main display will be a treat.
I had him in the display for a while and when I saw him picking in my first corals I took him out and sumped him. He also snapped at any fish that got close. I doubt he would catch them but I prefer a tank where I don't worry about aggression. I've been considering putting him back but I'm not sure

