Seems like the specks represent the algae that all of my plecos and snails don't really "enjoy" eating, they prefer fresher algae on the rocks or something. So my glass is usually pretty clean, but usually has little specks everywhere if you look close. Meanwhile the plecos are all busy eating other stuff.
I always use a razor blade now, because I scratched the glass on my
SW with a magnetic scrubber. I washed it first and everything but there was a hidden sharp grain of sand. SKREEEEK!!! Auuugh!
And into the dumpster it went... clunk.