Reef Builders - The Source for Reef Keeping Information

We are a new family to the whole reef tank thing. We've had our tank,55 gal., for about 6 months. I've noticed these new growths on almost all of our live rocks. The only way to describe them is that they look like little chimneys that have these strings coming out of them at night or when the water gets stirred up. Are these bad or good? I assumed they were good, since they are growth that we have not put in there purposely ourselves. Please don't laugh at my ignorance, but I've also noticed...

rarucas