i dont really know what type of algee it is i have had him for a while and i always warm my water before changeing so i dont think that it is temperature or my starfish may have suffered aswell lool. i think he may have starved thoe because i try n keep front n two sides of my tank clean so the snails n sea hair concentrate on the back wall and the rock but i have stoped cleaning the front of my tank for about 2 weeks now and it is still clean however there is a brown/dark green algee on the back of my tank. and red spots in my sand which i have no clue what they are, i picked one up and it was like a holow shell and crumbled in my fingers. i have no clue what it is doe.