Light spectrum used by algae

[rbv65]

am running a hangon refugium. I presently have Cautemorpha, and Caulerpa growing in it, but the Cau lerpa doesn't look well. It is lighted by two subcompact florescent bubbles. It was suggested that I place one 4100k 9W in to replace the blue one which was in the fixture when I got it. The other bulb is considerably higher in Kelvins and produces a much more blue light. I am wondering if I should replace it with another 4100k?

 

[taikonaut]

Only if you have other use for the blue bulb, or it is too old. The lower Kelvin bulb is more efficient for the algae, but there is no enough incentive to replace it right away and throw a perfectly fine blue bulb away.