1st. Time High Again: my experience has shown that you can grow as many plants as will fit directly under the T-5 light fixture. This is my major regret; that I didn't buy a wider T-5 light fixture. I was penny wise and pound foolish. I bought fixtures four tubes wide and now I wish I'd parted with a little more cash and bought the six or eight tubes wide models. All of mine are almost 15 inches wide and they don't light anything bigger than the size of the fixture adequately. Fortunately, my 10 gallon bubble tubs are only 14" wide when set end to end so my T-5's light up what's directly under it but when they really get big and start to grow out away from the light the parts of the plants at the edge of the light are a lot less vigorous. A single HID or HPS in my little tent would undoubtedly be more efficient but then there's the cost trade off of feeding those monsters. On a 4' long fixture four tubes wide I would think you could grow four to five plants without any problems. More than that could be overcrowded. I hope that helps. HSA
