Four of the six-tube, four foot long fixtures light my 10'x12' greenhouse very well, Kathy. It is about as bright as winter daylight at noon. These are all T5HO tubes. Four tubes are 6500K and two tubes are the 4000K in each fixture. They are mounted as close to the ceiling (9' high) as I could get them, about 6" from the ceiling. I ended up moving my top shelves down about a foot (they are now approximately 2..5' from the ceiling because the lights are so intense, they were beginning to cause some signs of early sunburn on the more tender Catt. orchids. I now have my orchids no closer than 18" to those tubes. I keep my seedlings no closer than 3' to the lights. It might be more like 4'. It will be interesting to see what my Adenium seedlings do under the lights, and how close they can be to them.
