What is this, algae, tube worms, coral???
 

Ok, this is what brought me to Reef Central, I hope someone can identify it, I dont' know if I should get rid of it or not. It's only on one rock, but totally covering the rock, the bumblebee snails love it and all of them are on that rock. It is a new tank (4 weeks old) that hasn't cycled yet, and the rock is also new (one week) but none of the other rocks that I got from the same place have it on them. This is a 90 gal tank, with 8 green chromis, one small Xenia coral, and snails and hermit cleanup crew. 30 lbs of rock, and 2 1/2 inches of sand. 2 1200 powerheads, external skimmer, Fluval 405 cansister filter. 2 x 96w lights (one white one blue) and one 40w regular florescent.

1) Welcome to Reef Central
2) To answer your question, those are hydroids. They are invasive and can be tough to eradicate. I'd remove the rock.
3) If your tank hasn't cycled, and the rock isn't cured rock, everything will die when your tank begins to process the organic material and produces ammonia and nitrites.
4) If you're running filter floss or similar in the canister, be sure to clean it regularly in a bucket of tank water or you will have excess nutrient problems.
5) If you're new to reefkeeping, be sure and ask questions before you purchase something rather than after. Good luck.

I'm by no means an expert but they look like tube worms more than hydroids. They look like hydroids too, but the tubes they seem to be coming out of is throwing me.

Do they retract into a hard tube when you pound on the glass or agitate them in any way?

actually, the color has me leaning towards hydroids. I believe the above poster was correct.

I retract my further response about hydroids.

I blew the picture up and noted that they appear to be coming out of "tubes". I'm going to say red fan worms. I've had them, but never seen them in those numbers in one spot.

A larger picture would be helpful, but after zooming on the picture, I'm leaning against hydroids, but with the size and quality of the picture it's still hard for me to tell. Some on the bottom even resemble aptasia.

Are the bases hard and calcerous or are they soft?

My guess is it's a serpulid not sabellid, because the tubes look calcareous. If when they hide they have an operculum (trap door) covering the hole I am probably right.

EDIT: They are harmless. Keep them!

They are tubeworms, which will not hurt anything but will eat food intended for your coral. I have some and they seem not to spread to fast.

Look like digitate hydroids or pom-pom hydroids to me.

Id say tube worms but Im not sure....

I'm going with tube worms

It should be pretty easy to tell if the tube is calcerous be feel. As noted, tubeworms are a cool part of the hobby.

Why would u put anything in your tank if It didn't cycle yet and I think for a 90 gal u should have at least four watts a gallon that is my personal choice good luck

Thank you all so much for all of your responses. Because of the conflicting responses I decided to leave them in there, and keep a close eye on them. It has now been about 8 months and they have not spread. They seem to have stayed on the rock. My yellow eyed kole loves to pick at that rock. I now have a much more stocked, and better set up tank. 760w a 40 gal sump, and 100 lbs of rock.https://picasaweb.google.com/1040587...59654900692690

They are hydroids but not one of the invasive species ime.

hydroids

So, are they hard or soft?

Soft, they don't blow around with the flow of the water but if you touch them, they are soft.

The entire thing (including tube), correct? If so, I am going to side with the hydroid judgement.

Entire thing

look like colonial hydroids to me. I had them didn't multiply for ages then went to t5's and they did get rid while there aren't many

Colonial hydroids.

I'd still like to see a close up before deciding whether they're feather duster polychaetes or hydroids.

Sorry, the rock is in the sump now.

good idea you can leave the hydroids there they shouldn't spread back to display as long as there are no more in it anyway.