Here's a corrected link for that previous post, which is the best page of its type I've seen out there...
OK... so the tank cycled fine, and you scrubbed the rock before curing it in your tank. I was thinking that maybe you didn't cycle and this was just the normal crud coming off your rock as things died off. Very glad to hear I was wrong!
That's really a bizarre video... you're right - there's a lot of those little stings flying around in there. Seems like whatever would've come out of your rock would've done so when it cured/cycled. Got me stumped.
If it were my tank, I think I'd be in there with a fine mesh net, scooping out as much of that stuff as I could on a daily basis. Running some GAC
(granulated activated charcoal) probably wouldn't hurt either, just to be on the safe side.