Barnacles, Snails or Something else

[alang_94526]

Over the past few weeks I have noticed a growing infestation of something that looks like tiny white barnacles on my glass. They are crunchy/hard critters that will scrape off the glass OK, but don't scrape off the overflow columns so easily.
I'm not sure what they are, how they came to be in my tank (since I haven't added anything to my tank for several years, other than RO water and salt).
I'd also really like to learn how to get rid of them.

My tank is a 135 gallon, marine fish only plus live rock setup with mostly tangs and clownfish.

 

[jimv8673]

probably copepods, copepods make excellent food for picky eaters like seahorses. Mandarin gobies love them and they are essential to a reef tank adding biodiversity.

 

[Sploke]

Are they hard and look like little circles or spirals if you get very close to them? If so they may be calcareous tubeworms. They are harmless, although generally appear in newer tanks and can indicate high nutrient levels.

 

[alang_94526]

Thanks to you both. I think they most likely sound like the calcareous tube worms.