Johnpaul have you tries using excel on mosses? Does it help them grow in faster?
In my tanks with mosses I do occasional, small doses of Excel. It certainly didn't hurt any and I suspect it did indeed help them. I have heard you can "melt" some mosses by overdoing with Excel; when I dose it, I dose it at about half the amount the bottle suggests, and rather than dose it every couple of days like the bottle suggests, I only dose it maybe once every 2 weeks. So, for what that's worth, that's my experience with it.