This showed up on my glass last nite, tank is about 2 months old. Did a quick search and it looks like nassarius snail eggs (yes I do a have a few in my tank), but these "sacs" look different than what I have seen in the past.
Those look like strombus or dove (aka nano conchs) snail eggs. These are pretty cool little guys and will reproduce. You'll find eggs on your powerheads, usually on the undersides and of course, on the glass.
