Are 'blue' lights just for visible color?

[Jeff]

OK, I understand the Kelvin temperatures and that you want to match your lighting temperatures to the livestock's requirements as well as having a good looking tank. What I'm not sure about is this:

I've heard the term actinics. Now, is any bulb, even if it's not visibly not blue, over 16,000 K to 20,000 K considered an actinic blub? Or is actinic specifically a blue cast bulb that makes the corals florese?

I thought also if you have a 14,000 - 16,000 K metal hailide blub then there is no real need for blue floresent other than looks?

This will probably all be covered tomorrow night in the lighting lecture but I was concerned about this one issue in particular.

 

[psteeleb]

@DheereCrossing wrote:

I'm not positive but I believe atinics are over 20k and pretty much only have blue. Other MH bulbs that are in the 16-20k range may give off other colors but have most of their intensity in the range defined.

For the most part atinics are for just looks, at least this was the thought up till just recently. I have seen a discussion or two on Reefcentral and was talking to Marc the other night about this as there appear to be some very recent thoughts that atinics may provide more PAR then they get credit for.

There are some people that run reef tanks under just 20k's. I suspect they have to have additional wattage or longer photoperiods to satisfy the corals or they may just not grow as fast.

So the answer is there is no real set answer. Other then; know your coral needs and try to keep them happy, and then know what you like and adjust accordingly.