Rock turning white?

[FrankB1]

Some of he rock top are turning white. All parameters are good. Maybe too much light with 250 W MH over a shallow 20? Calcium is at 420ppm. I have cut the light down in time. Any other suggestions?

[Jeremy B.]

That is very common, and really nothing to worry about. THe coralline will sometimes die back just a little, but will come back with no problem. Take some pictures of the rock work so you can back and reference them in 2-3 weeks time so you can note the differences that are happening in the tank.

Thanks,
Jeremy

[FrankB1]

Thanks Jeremy, thats reassuring so I leave my lighting schedule as is for now.