Question
QUESTION: I have a existing 700 gallon pond with 12 6" goldfish for nine years now. I built a 3500 gallon pond that doesnt have a filter set up yet. I have a small pump in the new pond to circulate the water and add oxygen. I need to transfer my fish before I set up my new waterfall and filter system.I checked my PH and the old pond is 6.2 and my new pond is 7.2 I heard I cant tranfer them with that much diff in the PH levels. I tried 3 apps of PH down and $30 later it didnt change. How can I lower my PH rapidly being there arent fish living in the new pond yet?

ANSWER: 7.2 is a great pH and you should be raising your old pond's pH, not lowering the new one's pH.  It is easier to do and safer.  Add baking soda in small increments until you are at about 7.  You may want to do a partial water change and discontinue the use of the pH down.  It is quite unpredictable and only works in certain situations.

The reason for the pH difference is most likely due to differences in alkalinity (aka carbonate hardness).

---------- FOLLOW-UP ----------

QUESTION: About how much baking soda and at what time intervals? partial water change on which pond new or old? thanks for the advice

Answer
It is hard to say exactly how much baking soda because pH is on a logarithmic scale, meaning that 6.0 is 10x more acidic than 7.0 and 4.0 is 1,000x more acidic than 7.0.  On the same note, a pH of 11.0 is 10,000x more basic than 7.0.

Because of this you want to add baking soda and decrease the doses drastically as you approach 7.0.

pH is a temporary snapshot of the ratio of hydrogen ions and hydroxyl ions.  These are not the only things in water (although "pure" water is H20) and you also find calcium, magnesium, carbon, and several other elements and compounds.  The amount of carbon in the water dictates the buffering capacity of the water.  A very strong buffering capacity would bring the water up to a pH of 8.3 (the pH of carbon) and any acidic compounds will tilt the scale back downwards to 7.0 or below.  The reason that the old pond is at 6.0 is because all of the carbonic ions have been used up in chemical reactions, effectively draining the buffering capacity, allowing the acidic compounds to drag the pH down below neutral.  Adding baking soda will alter raise the alkalinity (buffering) and cause the pH to go up.  Too much will make the pH 8.3 so add about 1/8 cup to the old pond, wait 6 hours and retest pH.  If you notice a huge jump, add 3 tbsp every 2 hours until the pH reaches 7.0 or so.  If you don't notice a change at all, try another 1/8 cup.  If you do the partial water change, it would be on the new pond to get rid of the pH down you added.  pH down doesn't work because pH is dictated by the H+:OH- ratio.  If you know high school chemistry, you know that this bond is pretty much unbreakable.  It must be altered by changing other variables, such as the alkalinity, concentration of acidic waste (urine, dying leaves, etc), and CO2 concentration.  The miracle pH products are bi-carbonates (such as baking soda) and Hydrochloric acid.  Best of luck in your fish transfer!