PH in my pond

Question
Hi Robyn,
I have a 300 gal. poly pond with a large koi (18"+) and 5 or 6 3" Comets. I have a bio filter that pushes water up and out of a cement center piece, it runs 24/7. My problem is ph. It seems that when I test, the ph level is very high. I use dip strips so I don't know the number, but the color is on the Oh Oh side.
I was using "Crystal Clear" ph reducer and it worked well, For some reason, Petsmart is no longer carrying it and it's even clearance from their website. I live in upstate New York and it seems every time it rains, my ph goes crazy.... What can I use to get my ph back into check without spending $20 a week? Can I use same ph reducer for my pool? I was told baking soda will work. I am concerned for my fish so I need advice from someone who really knows.
I also have 2 potted elephant ears in there, but they are not growing too well.
Any help will be appreciated.
Thanx so much!
Michael

Answer
Could the problem be your cement center piece?  Did you pre-treat it with an acid wash when you got it or made it?  If not, it's probably leaching and raising the pond's pH and hardness. Did you test the pond for hardness and alkalinity?  You should also compare that to the results for your tap water.  Baking soda will increase the pH and alkalinity and buffer the water near pH 8.4.  If your pH is off scale, it's probably already too high.  You may need to remove the cement or seal it with polyurethane sold to seal ponds.  Rain dilutes the water so that the pH and hardness go down.  You can buy hydrochloric acid (sold as muriatic acid at pool stores) or sulfuric acid (the one sold in pH down for ponds) to lower the pH as long as there are NO other ingredients in the acid aside from acid and water.  You can even use acetic acid (vinegar) in a pinch but it's not as strong.  The pH reducer solid sold for pools is not safe I don't think (does it say what's in it!).  Elephant ears don't particularly like to be in the water too much but should do okay.  If the pH is really high though, they would suffer from that.  I hope that gives you some ideas.
Good luck!

Robyn
fishpondinfo.com