I'm running a current USA 96w (4 x 24w) T5HO set-up on my 20g tall reef tank. It's been running with the stock lights which are 2 x 10,000k daylights and 2 x 460nm actinics. It's time for me to replace the bulbs and I'm wondering what my options are and what would be best in the opinions of some of you much more expereinced reefers that are running T5HO set-ups.

Current USA doesn't have many options in the 24" 24w bulb category so if I stick with their bulbs I'll probably have to go for the exact same set-up as I have right now with 2 daylights and 2 actinics. The only other options with them is a 6,700k bulb and a 420nm actinic.

In other brands I've been able to find Giesemann bulbs of varying colour temps. One is called aquablue+ and the description states: "60% actinic and 40% combination (15000K). Great as a stand-alone bulb, or in combination with Daylights or Actinic bulbs." I'm not sure if this means it's 60% actinic and 40% 15,000k or if the overall colour temp is 15,000k but that's what I'm assuming. Could I use 4 of these bulbs? How is the Giesemann brand? This would give me a slightly bluer tank than I have now I'm thinking but is that ok? Giesemann also has 450nm and 421nm bulbs available that I can mix in any combination. Any suggestions?

Also available are Aqua-Science, Korallen-Zucht and URI bulbs of varying colour temps (actinic, 20,000k, 17,500k, 14,00k, 10,000k, etc.) There's so much to choose from I can't decide. Looking for Ideas/advice. I'm ok with a slightly bluer look than I currently have but not too much.

http://www.nano-reef.com/forums/index.php?...t=0&start=0

^This. Color Temperatures are not what you should go by when choosing T5s. Likewise, getting "actinic" lighting is kind of misguided since there are many types of bulbs with portions of the blue spectrum.

Thanks. Guess I really should have started with that T5 thread. There's tons of great information there. Sorry for asking all those questions before reading that thread.

That being said, Lakshwadeep you mention that color temp isn't what I should be looking at when choosing bulbs, but isn't it an important part of getting the look one wants? BTW I quite like the look of your tank. Are you still running the sam bulb combo as in your fist post?

You should try to look at a bulb's spectral chart and maybe its PAR values. Unlike MH bulbs, it's difficult to whittle down a T5's spectrum into one color temperature, with manufacturers labeling the same color temperature for bulbs that appear very different. Color temperature is good only as a rough estimate of the apparent color of a bulb. I suggest reading the T5 testing pages link in the first post of the T5HO information thread for a generalized explanation of bulb types. In general, bulbs are chosen for growth (PAR) and coloration (i.e. bringing out fluorescence, reds/yellows, blues).

My current bulb combination is three ATI blue pluses and 1 UVL actinic white.

Thanks for the advice. Based on the research I've been doing and the fact that ATI bulbs son't seem to be available anywhere in Canada this is what I've decided to go with from front to back:

Giesemann Actinic +
Korallen Zuten Fiji Purple
Giesemann Aquablue
Giesemann Actinic +

with the option to trade out the Aquablue for a GE 6500k if I find the look too blue for my taste.

Any thoughts on this combo? Will I be able to delve into the world of SPS with this?

Fianlly, a problem I'm reading about my current fixture is that it doesn't have a built in cooling fan. I've tried searching but can anyone point me to a link for mounting a 40mm or 50mm computer fan onto one of these fixtures to help keep the bulbs at optimum operating temp. Thanks

Still no answer to my last couple of questions... Anybody?

And also, I'm planning on adding this screen top to my tank: DIY Screen Cover . Anybody have any ideas on how much of a negative effect this will have on my par values? Will it be less or more of an effect as having a glass top?

The bulb combo you mentioned is a good one.

I just made one of those DIY Screen Tops and I can tell you it will have little to no affect on your PAR.