Help if you can....

[HartfordWhalers]

So i recently bought a 70 watt JBJ MH. I put it over my 5.5, knowing I will have to raise it extremely high due to heat, bleaching. I have it about 15 inches above the tank. My ricordias Green birds nest candy cane mushrooms and monti cap are doing great. Yet my purple birds nest and my acro, both bleached. Why would it bleach they over the others, especially a purple birds nest over a green one. They are all on the bottom of my tank and the same depth from the light. None are being shaded by any rock. Yet some bleach and some didn't/ Any help or answers for me would be great

Thanks in Advance

Andrew

 

[SumBub]

What was your lighting before utilizing the MH? It could be light shock. How long before the corals bleached?

 

[Gwynhidwy]

The reason some bleached and others didn't is because corals are individual animals so some are more capable of dealing with changes than others, for a variety of reasons.

Your colonies that bleached might have been less healthy in some way, they might have had less light shielding pigment which could be from being in a lower light area of the tank previously, or being incapable of producing as much pigment as another colony, or simply be less protected because the pigment/color that colony produces does not block light as well, etc, etc. These types of variation occur even within one species of coral and can often be seen in different frags from the same mother colony.

There are many reasons this kind of thing happens and it basically comes down to the same types of reason that one person sunburns when another does not. It sounds like it was just too much light too quickly. Some people use various screens and shades between their new lights and the tank because it can be unrealistic to mount the lights high and slowly lower them.