Hello, i recently setup a saltwater fish tank in July. I put some instant ocean in it and i have a protein skimmer running, not much else although I'm supposed to. I have no living fish in it. I do have 1 starfish, 1 snail, and 2 crabs. I also have 1 live rock and 3 smallish coral rock. About 4 weeks ago i spotted a small feather duster or anenomoe looking thing growing at the inlet of my filter system. It has grown some since then, so i know it is a living thing. it has tentacles of sort and a base and is attached, but moves about. I would like to know what it is and why it has just randomly grown there. Thanks~!