Bleaching at the Base - help needed

[IMPERATORFAN]

I've had an a. plana for about 4-5 months now. It has always looked happy. Great PE like most plana's seem to have. I just noticed a pretty good amount of bleaching at the base. It's definitely bleaching and not STN'ing because I can see bleached polyps out on it. The rest of the coral looks like normal.

I've heard some people say low mag will cause bleaching at the tips. Any thoughts on what might cause bleaching at the base? I'm just about certain that it's not a temp/heat issue because I have had very stable temps for a while. The tank hasn't gone over 80.1 and it usually stays within 1 degree from day to night.

Comments? Suggestions?

 

[jjackson]

blocked light?

 

[IMPERATORFAN]

Has that caused bleaching for you in the past or do you know of that to have caused bleaching?

That's a pretty interesting suggestion because I just lowered my VHO's last week and they may be blocking some of the halide lighting on that piece.

 

[Wiskey]

I have seen policiporas that when they shadow themselvs badly enough the pylops that are shadowed go clear, I have also seen the shaded parts of montipora go white especially on the back side.

It sounds feasable to me.
Whiskey

 

[Charlie Davidson]

It has been my exp. that a sudden decrease in alk or low alk (never say allways) causes this.