Please help if you can. This is the first time i am having problems with algae and of all places it is growing on my plants and a spot or two on my glass which i clean right away. But the stuff on the leaves of the plants it is impossible to clean i tried gently rubbing it off with my fingers on some of the bigger leaves but no such luck.. can anyone help at least tell me what this nasty crap is and maybe some way to get rid of it that doesn't cost a lot or doesn't involve chemicals?