Liverock bleaching?

[noobzilla]

I've just noticed a couple white spots on the purple areas of my liverock. I recently did a 10% water change due to an unhappy candy coral. Everything else in the tank is thriving since the water change. I have been putting purple tech in, and forgot last night, could that be the cause?

 

[xcali1985]

Low Alk can cause this along with low calcium. Was the rock out the water when you did the water change?
I would check to make sure Alkalinity is in line first.

 

[noobzilla]

Just got back from a hike that turned into camping trip and tested all my parameters. Here's how things look:
Ammonia, nitrate, nitrite and phosphates are at 0
PH 8.0
Salinity: 1.031 (it went up while I was gone)
calcium: 460
Alk: 9 dKH
It doesn't look like it has spread any, still about a 1/8 inch circle on the rock it's on.
The rock hasn't been out of water since I originally put it in.

 

[xcali1985]

Alk is within range 8-12dKH, but I would personally try to get it closer to the 12. Your pH is probably dropping below 8.0 at night during the day you should try to get it up to 8.2-4 range. Adding Alk will help stabilize your pH also.

 

[noobzilla]

Ok, will give that a shot! Thanks for the info.