One more thing. How old are the T12s? Old bulbs can and will cause GHA. I thing I read that the MH bulbs where new. As far as removing rock if its got the flow between them and spaces like you said it might not be the problem. Get the GFO up and running but dont expect it to go away quick. it will still take a month or so. if you really want it gone then get a sea hare. it will mow it down fast. the problem is that when its gone the sea hare starves. I have never understood why A LFS didnt just rent sea hares out to people with GHA problems.
Yes my t12 are old. Just replaced them a couple days ago. The MH's are new, replaced a month or so back. I guess I will see what happens with the GFO running before I remove some rock. Thanks again !!
CD