Low PH in my pond?

I have three week old pond (1000 gallon). Initially the PH was 6.8 then within a week it dropped to almost 5. I did a 25% water change PH came up to 6.5 then in a day again dropped under 6. I have 7 Goldfish in it which seem happy. I can't figure out what could cause such a drastic dive. My only suspicion is the garden soil. I tested the garden soil and it is acidic. I planted all my marginal and lilies in it combined with aqua soil, and topped with gravel and tiny lava stones. They are planted in a fabric pot so it is very permeable. Any thoughts what could causing the PH dive?

Low PH in my pond?
I think you're right about the acidic soil. Rain is also acidic, so if it's been wet in your area . . . Do you test at the same time every day? The pH fluctuates throughout the day, so to get a good idea of what is happening in your pond you should.

Overstocking of fish can contribute, because they release CO2 which can become carbonic acid if water is saturated with it. Is there anywhere else you can keep some of your goldfish for a few days? Maybe that would raise the pH enough. Aerating the water (good, big splashes) will help reduce the amount of CO2 in the water also.

The plants should be helping to raise the pH. Since it apparently isn't enough, here's a link for pond product to raise your pH. Sorry, I haven't had this particular problem so I've never tried this product.

You should aim to raise the pH slowly, maybe 0.3 points a day, to give your fish and plants a chance to keep up.

Good luck

http://www.pondliner.com/pHUp.htm



Here's a source that goes into a lot more detail than I know

http://www.aquariumsite.com/freshwater/c...
Reply:Caustic Soda will lower the PH. Check the rate of application