so i have a 10 gall reef thats been runngin for about 6 months now. my question is what are all the little strings coming off of my rocks and out of the sandbed? i think they r tentacled of some sort bc ive seent live brine shrimp get captured by them. they also have the ability to retract into the rock or sand. what are these things? they are kind of unsightly bc of there numbers and im wondering if they could be bothering my corals. are they good? bad? can i get a critter to eat em?