Hello all. I have about a 1400 gallon pond with about 12 goldfish. I have 2 Iris, and a small pond Lilly, and some other small plants. The pond is surrounded with moss rock, which I am assuming is sandstone, I have some river rock of various sizes and some rip rap lining the bottom and sides of the pond. I am using a Savio skimmer with filter, and have a 10" aerating stone in the bottom of my pond which runs 24/7. My water pump runs only during the daylight.

I am getting green water and a little bit of string algae. I had some toads that mated in my pond, and I noticed that all of the tadpoles died immediately before leaving the slimy stuff they lay. That is what concerned me, so I did a full water test (pH, Nitrate, Nitrite, and Phosphorus). All is good, but my pH is off the charts (>9.0). I added some pics. I read somewhere that adding 1/4 cup of white vinegar per 500 gallons would help lower my pH. Does anyone have any suggestions? Is it possible that any of the rocks would cause this alkaline water?

Thanks in advance,


Mike

A PH of 9 is very high. It could be what caused the tadpoles die. However, in my experience with small bodies of water (aquariums and the like) adjusting Ph can be a very slippery slope. Especially depending on your alakalinty(the higher it is the more resistant the water is to Ph changes) A lot depends on the particular fish species you are trying to raise, but in my experience almost all fish can handle high Ph levels if they’re used to it. Much more deadly to aquatic life is sudden Ph changes. I do believe vinegar, which is highly acidic, will lower your Ph, but if you lower it too much or too fast you will almost certainly kill all aquatic life you care about. Like I said, my experience with lowering Ph is limited to aquariums, but I have always been told by experts to just leave it be, and when I did not follow they’re advice, I usually screwed up the chemistry totally. Hopefully someone who’s more of expert will give their input, but depending on your preferred aquatic life, I would definitely not rush to change anything at this time.

PH changes over the daily cycle. You need to measure alkalinity. You can try to take pH several times over the day early am . noon and dark and compare to see the change. Ag lime will help increase alkalinity. Alkalinity buffers pH swings. I am assuming this is a soil bottom pond.

See charts in this archive link.

http://forums.pondboss.com/ubbthreads.php?ubb=showflat&Number=96127#Post96127

Thank you both for the info. Sorry for the delay, I never got notified of the replies. The only thing I plan on raising in my pond are goldfish and possibly a couple of frogs.

@ ewest, my pond is EPDM liner, moss rock, which I am assuming is sandstone, various sizes of river rock, and RipRap, which I confirmed today was granite. Other than that, not sure what else could be doing this.

@ Cole B., When I get back from vacation, I will try checking my pH at various points within the day and report back.

By the way, I read somewhere about over oxygenating the pond can cause problems. Can this be true? I run my aerator 24/7.

Thanks again,

Mike

If you mean over oxygenating can cause PH problems, I have never heard of such a thing. If you mean problems in general, aeration can cause problems by mixing the water too much and preventing a thermocline, therefore making the entire pond very hot in summer. In such a small pond, this is not a concern because the water should be basically the same temperature throughout no matter what. I don’t know what the water is like where you are, but in west Texas where I’m from, the water is extremely “hard” (high PH) no matter what. As ewest said, your alakalinty is very important because it dictates how susceptible your PH is to change, both naturally and artificially. In my area, alkalinity is very high. Goldfish are very very hardy creatures, especially the common strains, so I would tend to suggest a “hands off” policy for managing them unless change is absolutely necessary. But my water chemistry experience is limited to a couple years as a “pool boy” and many years with aquariums, so definitely give more credence to the actual experts, such as ewest.
Best of luck,
Cole Byerly

I would also suggest testing the pH of your water directly from the source. For example, If you fill your pond with a water hose, test the water directly from the spigot or hose. I would suggest collecting and then holding the water for 24 hours before testing, as tap water in cities usually has chlorine added which can lower pH. The chlorine should dissipate into the air in 24 hours, giving you the most accurate reading. If it matches closely the pH and alkalinity of your pond water, there is not much you can do regardless. If it’s not, it is much more likely your substrate or other factors are effecting your pH.
Cole

I would try adding a little ag lime and see if the pH swings moderate.