PH refuses to go up!!

[Beermaster]

Really? venting it outside, made that much of a difference? I would have never thought of that.

[Skimmerking]

heck ya its getting pure fresh air to the water.. instant boost try it you will be amazed

[Beverly]

A quote from a very complicated article, The Chemical and Biochemical Mechanisms of Calcification
http://www.advancedaquarist.com/issues/apr2002/chem.htm

Implications for Reefkeeping: pH

It is well known in the scientific literature, if not in the reefkeeping hobby, that calcification is slowed considerably as the pH is lowered below natural levels.15,16 This result is especially concerning and is a hot topic of research because of the decrease in the pH of the oceans as CO2 is added to the atmosphere. The predictions of reduced calcification in coral reefs in the future are substantial. Again, taking the previous sections as a backdrop, we can begin to understand why.

As the pH of the external fluid is lowered, it becomes harder and harder for cells to excrete the excess protons that come about from calcification. That is, they take in bicarbonate, strip off a proton, precipitate the carbonate into their skeleton and then have to do something with that proton. Many of those protons can be used to make CO2 out of bicarbonate, and may thereby boost the rate of photosynthesis.1 Still, not all of the protons may be used this way, and some will be excreted.

Am not exactly sure what the pH is of natural seawater, though. Anybody know? What I'm understanding from the article is that low pH lowers a coral's ability to calicify.

The article also discusses Ca levels extensively, and phosphate, Mg and strontium to some degree. It's really better to read the whole article for the quote to make more sense.

[i have crabs]

why not add a ph buffer if you want it up ?
http://www.seachem.com/products/prod...eefBuffer.html