remember the more the merrier, LOL. They maybe able to veg, but since they are 4 ft they tend to spread the light evenly and thinly over a big suface. You may get tall thin plants due to over reaching towards the light because of not having sufficient amount of it. Give it a try, but be sure to have a good reflector setup cuz those tube bulbs will throw light 360, hence loosing a lot of good light, Bounce tha bitch back and youll be better off.
Some of my google searching tonight's has led Me to believe that's not necessarily true. The t8's supposedly put out more lumens. I'm still researching, as tomorrow I am either buying For the current and possible future t5 or t8's, or for something not optimal currently but in a few months will be mhs Edit It's odd, other forums seem to be at odds on this while everything here it seems says t-5's compared to t-8's all the way.
I use t-8 for veg and it works just fine as long as you dont let your plants get too tall (more than 1 ft or so) and keep the lights right above the tops. I tend to pinch the tops a few time to keep them short and make them bushy. After a few weeks they gotta go under the HID.
He is right about this one. Thats why T5's are more efficient to use then T8 and T12. Lumens per watt is what you wanna look at.
im using t8, 5900 kelvin, 4'x6 bulb fixture it puts out 192 watts. but i have it in a reflective tent. It's good for veg and seedlings. I have it hanging from those adjustable pulley hangers. I keep it close to the plants. i wish i had a t5 4 bulb its definitely brighter for less. i flower w/ MH and HPS 800 watt system. I used the MH 800 for veg last run, and my power bill was insane. good yeild veg'd for 10 weeks. 4 females Blueberry trees from spliff seeds.