Coraline

[Joe Sifuentes]

Coraline algae is getting white spots on the rock. Some of the spots if I get to early I can brush them off but over time it keeps coming back and eventually killing the area off!!
The wavemakers and some areas of the glass seem to be growing coraline fine..
Has anybody had this happen before? This reef tank is around 17 years old..

Parameters are 9 for alk and around 420 for calcium and mag around 1300
Nitrates 10-15 and phosphate minimal
I dose two Part on this tank and use iodide and strontium along with weekly water changes.. Corals all look pretty good.
Any suggestions of what could be causing?
I plan on doing ICP test but just thought someone here has maybe seen this..
Thanks in advance

 

[blaxsun]

I get white spots - but it's from some of the fish grazing on the rock.

 

[Fishy888]

The same happens to me too.

 

[taricha]

sorta looks like new coralline types spreading and growing over established. This happens regularly too.

 

[Randy Holmes-Farley Verified Community Expert]

I agree. new coralline growth is often white and I'd stop brushing it off. :)