those "things" are shells encrusted over with bryzoan
or actually to are shells one is rock... i have a couple snails in there too just for the shameface (they eat snails) i just fed him one
troy srry but i dont have a mandarin yet lol
im gonna get one but i dont have one yet. if u can visibally see the copepods on your glass and you think your tank is ready, give it a shot. i know people have kept mandarins in 29 gallons so i bet you could. what other things do you have in it?