Acropora polyp tips bleaching after changing kelvin

[ashish]

So after running 20k bulb for about 3 months and seeing my corals and clams browning up before my eyes. I decided to change half my tank to 12k reeflux 250w bulb under the light hungry corals. For acclimation I moved the light fixture about 8'' higher and reduced photoperiod from 9 hours to 6 hours for about a 2 weeks. One of my older staghorns polyp's began to bleach but just some area's that seem to be more exposed to lighting.

Everyone thing else seems to be fine. My 1 month old monti cap seems to be bleaching from the bottom and I really have no answers for him as it's on the 20k side. Ahh the sensitive sps species drive me nutts.

what to do?

 

[Paulca916]

When you changed to the 20k bulbs did you cut back your lights ?
How old were the bulbs befor you put the 20K bulbs on ?
FWIW I ran my MH only 4 hours a day my actinics 6
But I ran my MH's 9 months then changed them when I did change to new bulbs I cut them back to 2 hours a day increasing them a half hour every week until I got back to 4 hours a day.
Have you checked your ALK lately ?
Just saying if ALK gets high you can burn the tips IME

 

[ashish]

20k bulb's where only 3 months used.

I usually take acclimation to the extreme but did not in this case and payed for it.
12k bulbs are so much brighter and nicer then the 20k. Tanks with extremely bright colored corals can pull of the 20k look but my tank looks more natural with the 12k. My clam brighten back up in a week.