i have one already its set up i have a couple large peices of live rock in there with one horse shoe crab about 2 inchs, and one diamond spot goby which is taking pellet food

.... i have a heater, bio wheel filter and a new magnet power head (Koralia) that has a flow rate of 400 GPH, 1500 L/H .. is that good? do i need another power head? and i have a couple of snails the goby is a GREAT sand sifter. o and i have some brown algea thats forming so i got about 15 snails and i have a 96 watt light...