I have this crap growing all over my tank, but only on my plants and my driftwood. Not on the glass, not on any of my equipment. It is especially bad on a few of my plants, my frill and my cabomba. It is slimy and brown. I have a 29 gallon, with numerous plants in it, frill, cabomba, ludwigia, a few fish, 3 cardinal tetras, 4 julii cories, and a single red crystal shrimp. I am running a API Rena XP3 with the two sponges, a full bag of carbon, a bag of Fluval Clearmax (for nitrate removal), and Rena Biochem Stars. I have one 54 watt t5 plant bulb over the tank that runs 8 hours a day. I do an 8 gallon water change every week, with gravel vacuuming.

Can someone tell me what it is? And maybe what I am doing wrong, to correct the problem?

I will try to post a photograph of it.