rock turning white :-(

[debbie]

What causes live rock with purple and red/purple algae to turn white?
My snail is all over this rock cleaning it but I am worried that i now will have just plain looking rock with no pretty purple algae.
My lights are 2 self balasted 13 w bulbs. The tank is a 10 gal
:help:

 

[jlem]

What are your calcium and PH levels? If you replace those bulbs with 10K's you may have better growth and a bluer look.

 

[col]

Patches of corraline on my LR turns white from time to time. I have no idea why but it lasts a week or so.