For awhile, I have been battling low pH where it dips below 7.70. I have found it is a common issue in hot climates such as Florida and the fun part about living in an efficient and airtight house as CO² builds up in this type of closed environment. Short of replacing the whole house air exchange and heat pump, here is what I have done to help keep relatively stable pH above 7.70 in my 24 gal tank.

The Plan

First, test if it is an internal CO² issue and not another issue. Take a small sample outside and power an air stone in the sample for half hour to hour. If pH rises, then you have a CO² issue inside the house and need to resolve. For me, the following used together have helped stabilize my pH above 7.70 which was found by trial-and-error using feedback from other reefers and LFS and articles I have read:

• External air pump installed just under eaves (lots of rain here) bringing in air to an air stone in tank sump area. Drilled hole through side slab of house to enable this and used a nice face plate so wife not too mad and box & conduit on outside. If you have a nearby window, drilling holes in it or leaving window open may be better solution than drilling a hole through the side of your house.

  Cheap Air pumps do not hold up to well and I am on my third one in last year. I am using a more expensive piston driven one this time and crossing fingers it lasts.

  Please take note, you need to ensure the air pump location is in a location where external contaminants from pesticides or herbicides do not accidentally get introduced into your tank. For Floridians, don’t forget about Mosquito Control as their fogging may or may not be an issue. Use a special housing and pre filters if in doubt.
  

  

  Airlines from Outside
  

  1. Airline #1 from external air pump to air stone in back sump.
  2. Airline #2 from external air pump to air stone in back sump.
  3. Airline #3 to skimmer and not attached to air pump.

  
  
• Kalk Dosing using LM3 and controller which starts when the light cycle ends and continues till the beginning of the next light cycle. Ensure water level allows continuous dosing through evaporation or manual removal. Need to watch salinity if manually removing.
• Alk dosing using 2-Part in twelve increments throughout day using dosing pump and controller. My tank is currently requiring 50 ml/day of each Alk/Ca so this is helping. Until recently, I was not needing to dose this on a regular basis so I could not rely on it as part of my solution. Realize if you are using unbaked baking soda for Alk dosing, you will not receive increased pH benefit.

The Goal

Stabilize pH between 7.80 and 8.40 with only a 0.2 daily swing and maintain inhabitants good health.

The Hypothesis

Reducing CO² levels and buffering from Alkalinity and Kalkwasser will stabilize pH in optimal range using the natural pH photosynthetic swing.

Observations

Reef Aquarium Log (Excel File)
pH Raw Data and Graph (Excel File)

Conclusion

If any one of the steps utilized to control CO² issues by introducing external air, dosing Kalkwasser, or dosing Alkalinity fail, pH starts to destabilize. If two or more fail, pH dips below 7.80. Many of the high and low points for the pH Trend Observations are from anomalies such as Kalk ATO running out, dosing KH events, equipment issues, and poor monitoring and control of water change parameters. Therefor, implementation of additional parts of plan outlined above to control pH swings has improved pH optimal range while better husbandry practices and redundancy will decrease swing ranges and pH events.

DISCLAIMER: Your results may very as each system is very different from another. For my tank parameters and environment, this was my observations and conclusion. This was not a controlled experiment so there is a potential for a large margin of error.

References

Holmes-Farley, Randy. “Low pH: Causes and Cures.” Reefkeeping Magazine. September 2004. Reefkeeping. http://www.reefkeeping.com/issues/2004-09/rhf/index.php. Accessed 12 July 2009.

Holmes-Farley, Randy. “Reef Aquarium Water Parameters.” Reefkeeping Magazine. May 2004. Reefkeeping. http://www.reefkeeping.com/issues/2004-05/rhf/index.php. Accessed 12 July 2009.

“Kalkwasser Instructions.” Bulk Reef Supply. http://www.bulkreefsupply.com/a1/Kalkwasser-Instructions/article_info.html. Accessed 12 July 2009.

Medeiros, Mike. “Concentrations of CO2 in the home.” Reef Central Forums. 14 December 2008. Reef Central. http://reefcentral.com/forums/showthread.php?s=&threadid=1530009 . Accessed 12 July 2009.

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