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The pH in my pond is around 8.4. All other water tests are fine (no ammonia). I have a cement birdbath in the middle of the pond with flowing water. If this is causing the alkalinity to be high, what can I do? I don't want to take the fountain out if there is any other way to correct it. Sometimes it gets to around 8.9.

Fish are doing o.k..but I sometimes see some scales in water at times. I have done 20% water changes several times, but doesn't seem to help much. Any help would be appreciated. Thank You.

A pH of this level is harmless to ornamental pond fish, and only indicates that the pH is being supported by a LOT of carbonates.

These carbonates can come in your municipal water, or they can be generated by the cement ornamentation and concrete grouting of rocks and waterfalls. Ponds made of concrete traditionally have this high of a pH.

A pH this high only really matters when there are high accumulations of Ammonia because ammonia is much more toxic at a higher pH. Otherwise, this pH should be no cause for concern with ornamental pond fish.

Besides, if you apply chemicals to lower the pH, what you will see is the rapid deterioration of the bird bath as the applied acids eat away at the carbonates. As soon as the pH reducing buffers are consumed, the pH will rise again in less than twelve hours.

Reducing pH is a futile chore.

If the pond is REALLY high, or you're worried about the pH being that high, you can treat the concrete with a sealer which will make the concrete water proof and stop the leaching of carbonates.. There are several available.

Make sure whichever you choose that it's fish safe. Start your search for a sealer by checking out Hecht rubber in a key word search on the web.


Fish disease problems? Need some help? The help pages take you through the basics of the 'fish health work-up' diagnosis method and basic fish disease treatment methods.

90% of all health problems and fish deaths are caused by poor fish keeping! The key pages are essential reading for all beginners and intermediates who are serious about disease prevention.

Expanded Content by Dr. Erik Johnson, and Used with Permission; Frank Prince-Iles ©2009 All Rights Reserved