XM 20K or 15K?

[TheCoralReef731]

I was looking at some pictures of SE lightbulbs over tanks, and I found out that the bluer the bulb, the more I like the look of it. However, I also know that corals don't have the same opinion :lol: . Is there a significant difference in growing patterns between a 20K and a 15K. I have decided on the XM brand, but if anyone has a different brand, please share.

Thanks,
Peter

 

[Rod Buehler]

It will somewhat depend on the ballast you are drivving them with, but generally the higher the K the less PAR they have. IIRC, the XM15K is the exception to the rule though.. Im am pretty sure that their 20KK lamp produces more PAR than their 15KK..

This site may help.
http://reeflightinginfo.arvixe.com/

 

[TheCoralReef731]

Newbie question here...what do you mean when you say PAR? Is PAR good or bad?

 

[pondfrog]

PAR is photosytheticly available radiation----- a good thing if you are a coral!!

Basically, it is the amount of light available in the usable spectrum of light by our corals. The higher the PAR of a bulb the "more" usable light for a coral. Conventional thought is that, in theory, the more PAR a bulb provides the better your corals grow.
Now that's a HUGE generalization, meaning that some lower light corals might be "overlit" by a high PAR bulb, and it doesn't really take into account a bulbs spectrum, which will also influence growth rate as well as coloration.


In your specific question, if you like a bluer buld I would go with the 20K of that brand.. It is very blue and it's PAR is more than the 15K, but won't be too much, even for lowlight corals.

Steve

 

[TheCoralReef731]

Thanks, I am purchasing the 20K right now.