Algae. Looks like Cladophora.
Algaes are everywhere. They're on rocks, plants and even in the air. No telling for sure where it came from. My eldest stepsons have aquariums and have gotten all their plants from me. Neither of them has ANY plant in ANY of their aquariums that didn't come from me. Yet only Jeremy has staghorn algae in two of his tanks. Neither Mark nor I have any sign of it and neither do the rest of Jeremy's tanks. Weird, huh? No telling where it came from in Jeremy's. Could have been on a tank, some of the hardscape, maybe on a piece of equipment, from the air. It could even have come in on some plants and just found the perfect growing conditions in those two tanks, yet not liked the conditions in my tanks, Mark's or the rest of Jeremy's, hence none in any other tank.I have to wonder how I got something that is found in lake Michigan in my shrimp tank!!
Pick it out by hand. Sorry for the bad news, but that's about the best idea. I've heard that amano shrimp eat it, but I haven't tested that out yet. I plan to try them as I've got some of it in a tank of mine.Now the bigger question is how the heck do I clean up the shrimp tank without loosing all my valuable baby tears!?