haha you posted as I was posting.

I copied this from a website concerning the value 'k" as seen on most bulbs:
"K", refers to the color temperature of the light measured in oKelvin. A lower Kelvin rating indicates a warmer light source whose spectrum is more towards the yellow end. A higher Kelvin rating indicates a cooler source of lighting that emphasizes the blue end of the spectrum"

Basically the higher the oKelvin the more intense the light, and less the K the lesser intense, etc.

Ya plant websites are so confusing and sometimes contradicting. Unfortunately, when I bought my Hagen T5 HO fixture 2x39W, the LFS said it would be enough, but it most definitely isn't. I'm barely putting out 2 wpg. And my tank is deeper than 19" which also causes problems even for low-light plants. I cant even get java moss or fern to grow; which is pretty pitiful haha.

I do know a few good LFS in my area that might actually switch around bulbs for me, ill have to check up on it though.

I think what I'll do (depending on what Nobobo has to say) is purchase the 4x39W fixture in a couple of weeks, and do a test run to see if it's enough light. If it isn't Ill purchase the smaller T5 strip light as well, it's small and compact and would sit nicely behind the actual fixture. I hope the fan on the fixture isn't too noisy.

That's a good site with lots of information.

The part about CO2 came as a shock to me. Is it true that as you add more light to a tank you also have to increase the CO2 of that tank? I've been trying to avoid CO2 (it's damn expensive), but it seems that with my new fixture I will also need to compensate with CO2, and it's unavoidable?

Sorry for the gazillion questions everyone.

As far as I know Nobobo doesen't use CO2. I have a 65 watt X4 bulb fixture with three fans that looks like the second light you have a link to and they're really noisy when I turn them on. They get quieter after the light heats up, but they're still loud. I have a pretty high tollerance to noise and it would probably bother most people. I found a nice cooling fan in the garbage that is powerfull and silent and I use it to cool my lights as I have hidden them under a heavy cloth on top of my tank. PS Great link SWP! If anyone wants to forum with true planted tank enthusiasts join the www.plantgeek.com forum. These guys are really advanced and way over my head.

No worries bro, I'm curious too...

If I'm correct, it seems that the actinic bulbs do work for freshwater plants. Does that also go for the blue (not true actinic) light as well? I'm a little overwhelmed by all the different light characteristics, but that would make your shopping a little easier. Personally, I don't mind a little blue on my plants as looks go, but having more of a warm light looks better IMO. Those little clamp on halides for $300 or something are sweet as I've seen them in use and the surface ripples look really nice on the plants and other features in the aquarium. They're small, pack a lot of light, and are asthetically appealing to me.