High pH Issues...

[parallon]

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 have attached 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

Mike

 

[cas]

Hi @parallon . Did you test the KH and GH of the water? You don't want to try to change the pH directly, but controlling the KH and GH will stabilize the pH. GH will keep the pH lower.

 

[mrsclem]

Welcome parallon- How old is the pond? Do you have any filtration other than the skimmer? Your water pump should be running 24/7, any reason you are turning it off?

 

[Lisak1]

Like @mrsclem the thing that stood out to me was the water pump being turned off - is that the pump that runs your filter? If so you need to reconsider that plan.

Rip rap can mean just about any kind of stone - any idea what yours is?

Test your source water for pH - that might be a clue. Also test several times a day - morning and evening will vary. Pond pH will frequently lower naturally as the pond matures, so if it's not causing any issues with your fish or plants I'd be tempted to just watch it and see what happens. Our pH was initially off the chart too, but over time it slowly came down without us changing a single thing. The toads may have died for a whole other reason.

 

[MajorDan]

I have a new pond too and our water comes from wells in limestone so our water is HARD. So we had the same condition as you are experiencing. The water got very clear after about three weeks without fish and grew a pretty velvety green algae on the liner and rocks. High PH and GH and KH remained. We added fish and first pretty green algae died, water quality went south so we had to add Prime to protect the fish while microscopic algae took over pond to consume the fish waste that out three week old plants failed to do. The water got so full of algae you could not see the fish until they surfaced. We added more plants including some rushes to the bog and some submersibles, hogwort, mermaid plant and red luigia. The water gradually cleared as the plants started to get established. Lately the water got clearer and turned a stained brown, the hot weather arrived and the microscopic algae reappeared but not so much you can not see the bottom. I shared all this to say that our pond water hardness has dropped. KH from 400ppm to 200ppm and GH from 200ppm to 100ppm and our Ph is still 9. The fish are thriving and have grown from 3” to 5-6” in just a few months and all of the plants are doing great in the hard, high Ph water. We add 25-100 gallons of water a day using a timer and charcoal filter. The pond is 1200 gallons so the excess drains out the overflow.

 

[parallon]

Thank you all for the replies. Sorry for the delay, but I never got notified of the responses.

@mrsclem, the pond is about a year old now. It is EPDM liner. As for filtration, the Savio skimmer with filter is all the filtration I have. I spray off the filter every few days. Any suggestions for anything else easily implemented?

@Lisak1, as for the pump being turned off at night, not sure, just thought it would give the fish some peace, and didn't think much went on with the chemistry of the pond once the sun went down. I will set it back to 24/7 and see. As for the RipRap, I confirmed today that it was composed of Granite.

@cas- By the way, what is GH and KH, and how would I test for those?

We are on well water, but I will have to dig up the results of the water test when we bought the house. I have an auto-fill valve hooked up inside the skimmer, but no idea how much is added each day.

I also attached a photo of the inside of my skimmer a couple of weeks back with a lot of foam in it. Any idea what this could be? I also notice small patches of foam under my waterfall.

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 all,

Mike

 

[cas]

KH is what keeps the PH stable. Carbonate hardness (KH) will prevent low PH (a PH crash) and Calcium hardness (part of GH) will prevent high PH. There are test kits for both KH and GH.

 

[Lisak1]

I've never heard of over-oxygenating a pond. I don't even know if that's possible.

You need to run your filter 24/7, so if the waterfall is feeding the filter, that needs to stay on. When you turn off the pump to the filter the bacteria that are inside helping with biofiltration start to die off and that's not good.

 

[mrsclem]

Looks like your only filtration is the filter pads in the skimmer. Extra filtration will help. The foam is probably from the pump being off and the bacteria dying off.

 

[Lisak1]

Oh right - the foam is a sign of phosphates. Organic material dying and breaking down creates foaming.