High pH Problems By Randy Holmes Farley.
High pH problems in reef tanks are most frequently encountered when using limewater, but are also sometimes encountered when using other high pH alkalinity supplements, such as the original version of B-ionic. If the carbonate alkalinity is not more than 4 meq/L,
then high pH is typically caused by a carbon dioxide deficiency. Additives like limewater generate a substantial deficiency of
carbon dioxide in reef tanks, and the end effect is that the pH runs on the high side.
All of the discussion to follow presumes that you are using limewater (or other high pH supplement) properly. That assumption implies that you are adding an appropriate amount (i.e., balancing the rate of calcification, or less if combined with some other supplementation scheme) and that it is not being added too rapidly
(overwhelming the ability of the tank to buffer against pH rises).
One way to decrease the pH in tanks using limewater is to drive more carbon dioxide into the water.
One can drive more carbon dioxide into the water through better aeration, by adding carbon dioxide directly, or by adding an organic acid that eventually breaks down into carbon dioxide (
like vinegar; aka acetic acid). The vinegar can be added directly to the limewater itself, or directly to the tank.
Another good option to lower chronically high pH is to switch to an alkalinity supplement that has less of a pH raising effect.
Limewater is the worst of the lot, followed by sodium carbonate (washing soda). Sodium bicarbonate (baking soda) will actually have a very slight pH lowering effect on it’s own, and will make a big pH effect relative to adding limewater or washing soda. A CaCO3/CO2 reactor, of course, has the biggest pH lowering impact of any alkalinity supplement scheme (as described above).
Commercial alkalinity supplements track these suggestions, but there are too many to list. They cannot even be lumped together by class,
though most solids sold as “buffers” will have a fairly small impact on pH. Some two-part additives are largely carbonate and some are largely bicarbonate. To tell the difference, just measure the pH of the alkalinity portion. If it is less than 9, then it is primarily bicarbonate, and would be a good choice to switch to if chronic high pH is the issue. If it is more than 11, it is primarily carbonate, and would not be as optimal in this application.
Switching to another supplement does not necessarily mean a complete switch.
Switching partially from limewater to the new version of B-ionic, or one of the other two-part additives with a low pH impact can have a considerable long-term effect on pH. http://www.advancedaquarist.com/issu...e2002/chem.htm
High indoor carbon dioxide can also apparently lead to low pH problems in many tanks. Respiration by people and pets, the use of un-vented appliances burning natural gas (e.g., ovens and stoves) and the use of CaCO3/CO2 reactors can lead to high indoor carbon dioxide levels. The level of carbon dioxide can easily be more than twice that of exterior air, and this excess can substantially lower the pH. This problem is especially severe in newer, more airtight homes. It is unlikely to be a problem in homes like mine where you can feel the wind blowing around old window frames.
Many aquarists have found that opening a window near the tank can result in a significant rise in pH within a day or two. Unfortunately, those aquarists living in colder climates cannot readily open windows in the winter. Some have found it useful in these situations to run a pipe or tubing from the outside to the air input of a skimmer, where fresh, exterior air is rapidly mixed with the tank water.
Finally, the use of limewater in these situations is also appropriate. In fact, limewater may be more optimally used in this situation because the tank would be less likely to experience the undesirably high pH that sometimes accompanies limewater use. While limewater is the alkalinity supplement most potent at raising pH, other high pH additives would also suffice. Supplements based on carbonate, for example, would be very useful in this situation, while bicarbonate would not be. As a commercial example, the original B-ionic would be better than the newer version. For home brews, washing soda (sodium carbonate) would be better than baking soda (sodium bicarbonate).
Re: anyone have problems with Crushed Coral substr 
