Lighting requirement for live rock

[jester50]

Today I stopped by the lfs and for the first time discovered cured live rock from Molokai. Live rock is rare to find in Hawaii (legally at least), and the store just renewed their permit to start carrying on a limited basis again. So, I would like to purchase some.

Right now I have a 40 gallon tank with two 55 watt compact lights. One bulb is 50/50, the other is 7200k. Currently I am only turning on the 50/50 light and leaving the 7200k off. So I am getting about 1.3watts per gallon.

Question: What will I need to do to care for the live rock? Should I start turning on the 2nd 55 watt light for a total of 110watts? If so, what bulb should I purchase. 10000k? Or another 50/50? Also, do I need to add any sort of supplements? Or will the rock be fine just the way my set up is?

Im also running a bakpak2 bio and skimmer combo and a box filter.
Any help is appreciated.
Thanks!
Jessica

[OrionGirl]

Depends on what all is on the live rock. If you look at it and see coralline algae, it will fade unless you run both lights. It won't die, but will turn pale. If there are other photosynthetic organisms, their light needs would probably be met by your setup as well. Otherwise, the bacterial aspect of live rock (and the one most beneficial to your tank), needs no light at all.

[jester50]

Thanks for the reply.
There is coralline algae on the rocks which I'd like to keep. I havent seen too much other life on them except baby feather dusters. If I'd like to keep the purple coraline, I will run both lights, but what should my second light be? 10000k? or another 50/50, or a blue?
Also, I heard certain spectrum of lights will effect algae growth. Right now, I'm getting mostly brown algae (using the 50/50).
Im just worried the additition of the second 55watt compact light will make the growth worse?

[OrionGirl]

The other light will actually not impact the growth of brown algae. Brown algae are diatoms, which are not photosynthetic. The coralline algae will need more light--I would definitely turn on the 10,000K bulb. While you may see some green algae, controlling this with snails and hermits, and of course by limiting the food source is fairly easy. The coralline algae also needs stable calcium levels above 380 to really grow. You may be shocked at what all comes out in the higher lighting! Lots of 'critters' go dormant in low lights, and then spring to life given the chance. Cool stuff to watch!