color changing corals

[freshstart2008]

about two weeks ago i started using 2-70 watt mh's along with my 5-vho's,using a less lighting frame for the mh's to slowly get my corals to adjust to the new lights--i have over four colonies of gsp in my tank, but only one colony( the one that does not sit directly under the mh's) have changed colors to white--the polyps still come out all day, but they are white, the base of it is also white and the polyps are a light green instead of the darker green that they were---what could possibly do this, surely not the mh's?

my parameters are:
calcium---460
alk----5.5 meq
magnesium---1400
ph---8.2
ammonia---0
nitrate---0
nitrite---0.10
temp---81.3

anybody have any ideas about my gsp's---no other corals are affected, in fact they are thriving

 

[just dave]

You are using glass UV shields with the bulbs, right? In other words no light from the MH is getting out of the fixture without going through a UV filter?

 

[Rendos]

Double ended MH bulbs lack a UV shield that the single ended (mogul base) bulbs have built in. If you removed the glass from under the 70 watt MH bulbs, you removed the UV shields and are letting UV get to the corals...and fish. Reinstall the glass under the bulbs if you have removed them.

 

[freshstart2008]

no--the glass always remain intact?

 

[OneReef]

Alkalinity looks too high to me. May not be the cause of your color issue, but it does seem high.

 

[aslavatortin]

If you were just using VHO before and are now using MH, then yes the MH can definitely cause bleaching. Is it possible to move the GSP farther down in the tank until it has time to acclimate? FWIW, some corals will never adapt to being directly under halides. You could also try shading the colony...

 

[freshstart2008]

no way to move it-- but it is partially shaded by the large montipora

 

[aslavatortin]

<a href=showthread.php?s=&postid=14257921#post14257921 target=_blank>Originally posted</a> by OneReef
Alkalinity looks too high to me. May not be the cause of your color issue, but it does seem high.

Yeah, holy crap, totally missed that--that's over 15dKH!!! That can't be right...

 

[Rendos]

70 watt MH's are not very strong lights at all. I can't see that being a problem. The VHO's are probably higher in PAR than the MH's.

 

[aslavatortin]

<a href=showthread.php?s=&postid=14258937#post14258937 target=_blank>Originally posted</a> by Rendos
70 watt MH's are not very strong lights at all. I can't see that being a problem. The VHO's are probably higher in PAR than the MH's.

Fo' shizzle, I didn't pay any attention to any of the numbers in the original post apparently...I'm still waiting to find out if his alkalinity is really 5.5 meq/l, or if he meant 5.5dKH, or if the number was a typo all together....

 

[scarson61]

must be a typo because the Mg and Ca could not be at normal levels if the Alk was that high, something would be out of wack, Are you getting large temp swings since adding the new lights (just a guess and another thing to check on)

 

[arnjer]

Do GSP use chlorophyl<sp>
It almost sounds like they have expelled it with the light change
Seems like I read somewhere that some corals do that and then turn back to normal color

Jerry