Pets or pests?

These things have been popping up all over my tank... They appear to be in a small red tube with a spiderweb-like thread coming from it. They seem to be fishing or something as if something gets stuck in the thread it gets pulled back to the tube. There is some kind or worm or something in the tube doing said pulling. Anyone know what these things are and if I should be happy or sad to have them...

 

They are vermetid snails. If you have a nutrient rich tank (overfeeding and the like), they may increase to plague like proportions and irritate corals. Other than that, they can actually help and be a part of your CUC as they eat leftover food from overfeeding. Enjoy them for their biodiversity

 

Thanks for the quick response... I'm still a bit of a newbie. They aren't too annoying, and there are certain places they congregate, so I'll probably only go after them if they are irritating my corals...