Hi, hope someone can assist, as you can see from the picture, there is some fine grass like algae that appeared on my wood, it seems to be spreading at quite a rate. I've tried vacuuming it off, and also had a toothbrush on it, all to no avail, it seems really tough. Will reducing my light hours help, or is something else. It didn't bother me when it was on the wood, but it seems to be growing on some plant now. Any advice would be greatly appreciated. Sorry about the photo quality.