Plants will grow well under anything between 5000K and 10,000K. I run a combo of 6700K, and 10,000K. I am gradually changing the 10000K for 8000K bulbs.
I found 4 65 watt 7200k bulbs for sale on the internet in new condition. I figure I can put two on my 40 and maybe make something and put two on my 75.
Be careful with those cheap CF bulbs off eBay. I bought some and they really do not seem to put out as much light as Coralife or Current. They also do no last as long.
That being said, I agree with WyldFya; 7200K will be great for a planted tank, it's a little more "blue" than the 6500K's, which I like. It gives you about the same look as 10000K/6500K combo bulbs (my favorites.)
Hey thanks for warning me about buying bulbs off ebay. Maybe I will forget that and just stick to using the 50/50s. Part of 50/50 bulbs is 10,000k I believe. A 40 gallon breeder is shallow in height, so I don't need a ton of light. 2 50/50 65 watt compacts should do the trick. THanks!
I still would get rid of the 50/50 bulbs. They won't do that much for your tank. 2 6700K bulbs will do a lot more, or if you don't have enough nutrients, then 1 6700K over a 40G tank.