That is the very rare plastic star nematode. I haven't seen one of those since......about 3-4 months after I bought a new heater....I think they multiply quickly as the heater ages. Sorry, I couldn't help it.
You were not alone in the worrying about that. I started to notice little blue specks on my sand and was freaking out thinking it may be some weird bacteria or fungus. Cleaned them up and noticed more. I got evn more freaked until I looked at my heater and noticed it's pattern was off.