alkalinity mystery

[jmw31967]

I am stumped! Tank is 10 months,pollutant levels are all 0ppms, 170 total gallons, lightly stocked on fish and coral, 280lbs. lr, 900 watts mh lighting, alternate sump light cycle with lr in sump, and via aqua sk-388 skimmer, carbon filter before return, 6 stage ro/di reading 0, uv sterilizer in sump. My alkalinity keeps droping to 5 dkh in turn dropping ph at night to 7.9-8.0. I bring it up, and by the end of the week it is down to 5 again? 10g water changes weekly! What the !@#$#@!!!

[Randy Holmes-Farley]

[welcome]

reef aquaria normally drop rapidly in alkalinity as corals and coralline algae use calcium and alkalinity. So you should expect to have to dose calcium and alkalinity more frequently than once a week. Most folks dose daily.

This article has more:

Reef Aquarium Water Parameters
http://www.reefkeeping.com/issues/2004-05/rhf/index.htm

[jmw31967]

I add reef builder in top off water daily, and my calcium is 500 always?????, and when ph is low i add ph 8.3 both products are seachem. Thanx for the reply! what do you think?

[Randy Holmes-Farley]

If the alkalinity is dropping, you need more alkalinity supplement. Try more of the Reef Builder. :)

Stop the Marine Buffer. It is not a good product for reef aquaria, and is certainly not the best way to raise low pH. This article has more on low pH:

Low pH: Causes and Cures
http://reefkeeping.com/issues/2004-09/rhf/index.htm

What salt mix are you using? Some have excessive calcium to start with (like Oceanic).