I just bought a new fixture for my 46g bowfront tank, it's an Aquatic Life dual 39w T5HO. It came with legs that put the fixture about 4" above the top of the tank, which seemed excessively high to me. I took the legs off and now have the fixture on the very top of the tank. What kind of lighting do I have? I'm thinking medium level light, but maybe I'm wrong, maybe it's on the verge of being high light? The tank is pretty decently planted with a ton of java fern, some newly planted dwarf sag that is putting off nice vibrant new growth, some crypts and some ludwigia, and a decent sized sword plant. My substrate is dirt with sand cap. I'm getting diatoms which drive me nuts. I never seem to get any green algae in any of my tanks, just diatoms. I just started slowly introducing Seachem excel as a carbon source. My photoperiod was ten hours but i just knocked it back down to 8. Any advice would be appreciated.