try to get the daylight ones i got the regular ones and its kinda yellow looking.. i have mine in a trouble light.. the metal dome like things.. i have 2 on a 46 bow with a 10g hood with screw in flouressents also with a glass top works fine..
I had to take the reflector out of the hood (20") to fit 2x23 watt 5500K spiral fluorescents, but it works great. Beware, however, that they heat up but good.
I found a CF bulb at Lowes that will fit in the narrow All-glass hood without alterations. I posted the info a while back, still have the picture. The bulb-base and spiral are a smaller diameter allowing it to replace the bulb on the left. If you remove the reflector you have a lot of wasted light.
I also had to remove the aluminum reflector in my hood to make the new bulbs fit. To be honest, the oxidized aluminum reflectors in my hood can't have been that much better. That said, I am looking for mylar or something that is very low profile to glue to the inside of the hood. I may just end up going with the white Krylon for-plastic paint.
I bought a 4 pack of 14 w compact flourescent sunlight bulbs at Fred Meyer (Kroger's) for $9.95 this weekend. They're great. Not yellow like CF bulbs usually are and they're smaller than the 13w CF bulbs that I've bought in the past. They're made by Lights of America.
A few months ago, my local walmart had 20w 6500k CF made by Lights of America. These were the type with the straight tubes instead of spirals. Sadly, I have not been able to find them since, so when my current bulbs wear out, I'll have to use the spiral bulbs I ordered from 1000lights.com.