brown circle/patch on my live rock

[mrcopitr]

Hi guys,

I seem to be getting some kind of brownish circle/patch that expand on my live rock....is this another algae cycle in a new reef (my tank is 4 months old, ph 8.3 to 8.4, nitrates 0, ammonia 0, phosphate 0, I doze kalkwasser daily). And I also do 20 to 25 water change bi-weekly.

Have you guys experienced this type of problem, if yes what can I do to correct it....

Hoping to hear from you soon,

thanks...Marco