Using Multiple Light Sources

I've recently purchased a 400w HPS/MH setup but I am wondering if I could still use CFL bulbs in addition to that? I mainly would like to know if I could use 2,700K 5U Tube Compact Fluorescent LongStar Light Bulbs in addition to the HPS 400w during flowering. Thanks for your help, all.

of course. Over 3ft your 400w wont penetrate any deeper so they would make great side lighting for lower buds etc. Happy growing

Put em on the sides, just make sure they don't block the HPS light.

So I installed my 400w HPS today. It's down on one plant because the other died for some reason. Anyway, I'm wondering if you can have too much lighting? I'v also decided to use CFL's on the sides. I have 2 250W CFL equivalents on each side = 4 total making 1000W and then 1 150W CFL equivalents on each side = 2 total for 300W. So I have a total of 1700W shining on my girl. Could that be too much?

The CFL wattages are measured by their actual wattage, not equivalent. Anywho, If it's just one plant I think that's a ton of light! My single plant is under a 250w hps and happy as a clam