on this i am very lucky this is my first ever saltwater tank and when i bought it i was under the assumption i was buying just rock, protien skimmer, tank, lights, and a couple of snails. Got it all home and began aquascaping bare handed!! I actually brushed several of these off. I thought ot was some kind of algea. Only after reading about the bristle worms in my tank did i discover about the toxicity of things that are or can be common in reef aquaria.