retracting hair comes out of a tube

what is that thing, it has several legs that comes out of the hole and they are like white hair. thanks

 

Don't know the name but it is a worm and it is perfectly safe.

 

some type of feather duster. very common and just filter feeders

 

Did it make a kind of cocoon out of the sand? Spagheti worm maybe?

 

yes it made a tube of sand and its stretching out, sticking on the rock then pulling back. is it good or bad?

 

Does it have many "tentacles" or just two? if it is many, then it is most likely a "spaghetti worm". If it has two distinct tentacles, then it is a "hair worm".

Here's an article about them both: Spaghetti and Hair Worms

They are good for your tank, as they will feed on small uneaten particles of food or detritus. They can become a nuisance in a sand bed if they become extremely prolific because they can cause the sand particles to clump together with a substance that their body secretes, cementing the sandbed into lots of small "tubes". If that were the case, it would be indicative of other problems the tank may have such as low flow, detritus buildup, or overfeeding... Otherwise, these are harmless, very beneficial scavengers.

 

thanks this was helpful, probably they are the spaghetti worms but in my tank they are showing less arms than the picture in the article. when i stir the sand i find some tubes in there but scattered and not in high numbers. but anyways the sand is holding together but it can be stirred easily without having to break any clusters.