I use the GE brand 23W and they work good. I'm using 6 when in flower I'm going up to 12. For two plants. The lumens are 1610 per bulb for 6500 k and 1760 for 2700k. I think people may have problems because they don't make a hood to focus the lights or they try to grow too many plants with too little light. 6 lights per plant is good. I almost bought a huge 6500k cfl from home depot , I forget the name of the brand.