Photoperiod and Coloring of SPS

[ReefStar]

I run (3) 250w Metal Halides on my 125. I had a growth of some unusual algae/bacteria on some rock so I decided to shorten my photoperiod to 4hrs per day for two weeks. It caused the algae to die but also had another effect on my tank. Near the top of my tank are 3 SPS corals that have were pretty much white due to bleaching in the past. They had encrusted to the rock, so I could not move them unless I broke them off. After changing the photoperiod down to 4hrs, each one starting coloring up. One yellow, one green, one purple. This after staying white for almost 6 months. My question is this:

My halides (Iwasaki 250W) are 4 inches above the water line and these corals were 3-4 inches below the water line. Everyway tells me you cannot over expose SPS corals. Is it possible my standard 10hr metal halide photoperiod is/was too much because the bulbs are so close to the water line. In other words, should your photoperiod be relevant to the distance the bulbs are to your water line. So, if reefer A has 12" between water line and bulbs and reefer B has 4" between water line and bulb, should the photoperiod be different? I am trying to understand why these corals starting getting their color back. And what will happen when I go back to 8hrs per day??

Any ideas?

 

[Mac1]

Sorry Joe, but I don't have an answer for you. My experience with a few of these buggers doesn't help you either...

My 250 Watt Iwasaki's are about 2-3 inches off the water, with glass shields in between, and I have a piece of Green Porities, a Serioptora, and a couple table Acro's all within 3-4 inches of the water level, and they grow fine and like the light. Colors have changed since I got the frags, but they were in a 50 Gal lit by a pair of 400 Watt Hi Kelvin lights... Also a Pink Poico frag from Adam Cesnales that's starting to kick ass, and his tank is lit by 400 Watt Iwasaki's...

About the only thing I Can think of that might be having an impact, is the glass shields I run inbetween... They do block some of the light, and more importantly, the UV... Might want to try placing a small glass shield over part of the tank, and see if it impacts anything.

- Mac

 

[ReefStar]

I would imagine the glass shield cuts down part of the light intensity. How many hours do you run your lights?

 

[esmithiii]

Sounds like a good question for Galleon.

 

[cubera]

Hi, Joe. SPS can be over lit especially if they are not properly acclimated. They will burn and bleach with too much light too fast. You have proven this with the recoloring of your corals when you backed off on the lighting. IMHO you should ratchet up your lighting by 1/2 hour per week until your corals can tolerate 8-10 hours of MH. When we have this problem we put the corals under VHO or low intensity MH until they heal (usually a couple of weeks). Once they are acclimated they can tolerate being blasted 8-12 hours a day

HTH

 

[ReefStar]

Is there a big difference between exposing SPS corals to 8 or 12hrs of metal halides per day?