My tank is done cycling and the wonderful brown diatoms are starting to grow. Ammonia and nitrite are 0 but nitrates are 40ppm. I did add some fern culerpa that is starting to grow also. So, when can I add critters like turbo snails, blue or red leg hermit crabs and starfish (I like the Orange Linkia on sale from SWF)? My tank is a 28 gal bowfront with 2 small fish, live sand but no live rock. I do plan to add live rock slowly to this tank. Thanks!