Looks like hair algae. You'll want to treat that asap before it gets out of control.
Even if you throw it out, and get more, you'll have it in the tank. And when it dies, its even worst, red/brown hair algae all over your bottom. I'm dealing with it in my carpeted tank. That crap is all over the carpet, and it's really hard to get out even when when it's dead, it sticks to everything. Hard to remove without disturbing the carpet.
Treat your tank with some Excel. If you can pull your plants out, spray with some water mixed with hydrogen peroxide in a spray bottle. 10:1 should be good. Then just gently rub the algae off. If you want, you can give it a rinse in tap water, the chlorine will kill any remaining stragglers, before putting it back in your tank. Just keep your lights on for the minimum for a little while, and do regular water changes.
Mine started like that, within a week, every piece of surface was covered in that stuff. All the plants, driftwood, rocks. I had to spot treat the entire tank, it almost killed all my vegetation, since light wasn't getting to the leaves. Its recovering now, but still have a mess on my carpet.