HELP!!! What The Hell Is This Stuff???

[MMAX]

Picked up 3 fairly good sized turbos today. They started working the minute I put them in. For the most part the algae hasn't come back....yet. There's still a few tufts of it around so the snails should be able to take it out quickly. Hope to hell I get lucky and have this thing beat. Tested my water yesterday and phosphates and nitrates are next to nothing.