New pond high PH Mosquitoes and dying goldfish - HELP


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Last summer I had a pond built in my backyard. It was cemented in, and surrounded by blasted rock. It has a simple sump pump creating a waterfall effect.

Since the pond was installed, the water has at no time hovered around neutral ph. Our tap water in Victoria, Canada is perfectly neutral with little to no treatment. The water gets very murky quickly, and the PH creeps up to the 9 + level quickly.

When the pond was first built, it was cured (I don't recall how long), but then it was filled with water. The cement was not sealed with pond paint or the like. The first time I knew something was wrong was when I dropped in 8 fish, and they all died overnight. I tested PH shortly after that and I believe it was in the 10 range.

I subsequently drained the water, added new stuff and proceeded to dump muriatic acid into the pond for weeks to see if it would ultimately penetrate the cement and stabilize. That stabilization never happened (however the muriatic acid did bring ph down to 5 or so after each dosing).

Recently, my stone mason emptied the pond, and painted/sealed the pond with pond paint. I thought this would solve the problem as it was my guess that lyme from the cement was leeching into the water. It didn't solve the problem.

The PH looked to be close enough to 8, so I put more fish in. Fish died again.

Right now the pond has a lot of mosquito larvae breeding in it and I wanted the fish to deal with this situation. I cannot dump chemicals in to kill mosquitoes which will not kill the fish.

I am completely at a loss for why the PH is rising so quickly.

Please help. I am aware that the sump pump may not suffice in the long run as there is no biological filtration, but the acid in the water ought not to be spiking so quickly.
 

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Have you tested for ammonia? Number and size of fish?
 
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Have you tested for ammonia? Number and size of fish?
Have you tested for ammonia? Number and size of fish?
I think Craig has no fish as they die when he puts them in the water within a day. Also the high PH number indicated very alkaline water so hard to imagine it is ammonia I would think. I suspect it is the cement or sealer or both. THere is something that is messing with the water chemistry. I notice the pond has small water volume but high contact area with the rocks and presumably the concrete/sealer. High surface area to volume ratios can lead to rapid change in water chemistry due to contact contamination.
 
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that's what you get from reading from a phone and old eyes.... :cautious:

I agree with Ray on the pond leaching alkalinity some where. The rocks are granite? What type of cement and sealer was used? Do you have pictures of it being built?

It's been a while since the pond was built so I'm also surprised it hasn't cured to accept fish.
What is the longest you have cycled the water in the pond before adding fish? Typically it's at least a month. More so in complicated cases like yours, there's really no short cut to doing it the right way.

Try draining the pond and add some treatment to control the mosquitoes as it will be a few weeks before you can add fish. Test daily and report back here after two weeks. Drain again after 2 weeks if the pH continues to rise. If it doesn't, add some plants to help with the nitrogen cycle. After still stable after 4 weeks introduce a few comets, they eat mosquitoes like cracker jacks.
 

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@craigvee
Sorry this is happening to your fish. Could something be leaking into your pond from around the edge? I would also check the ammonia levels w/a good test kit. Do you have a lot of algae as that can cause ph to rise. From looking at your photo tho it does not look like you have a lot of algae. You have no fish now so you need to let this pond settle and cycle all over again. Keep testing the water for a long period of time and make sure tests all stay in the safe zones before adding more fish and add just a couple. You also have a lot of rocks in there and I wonder if they are all pond safe.

Taken from the net:
During the day algae will use sunlight and carbon dioxide for photosynthesis, and the removal of large amounts of carbon dioxide can cause an increase in water pH level and drop in acidity.
 
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Thanks for your replies. I doubt it's ammonia, and for your information the pond is 500 gallons and the most recent batch of fish were added after a near complete water change.

It could very well be the rocks in the pond, they are not specifically pond safe and are blasted rock which were obtained by my stone mason.

There is no algae in the water.
 
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There is no algae in the water.

That's an interesting detail - high pH keeping the algae from growing maybe? A standing body of water should grow algae.

Did you treat for chlorine after the water change and before adding fish? Just trying to cover all the bases here. Fish that die that quickly does sound like a pH issue though.
 
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Hello, Algae does eventually grow, particularly on the surrounding rocks. Indeed the water is very murky in just one overnight since a water change. The PH is 9+ so that would make sense why the fish would die.

I did not treat for chlorine because it is my understanding that we have very little residual chlorine in our water. For reference, I used to have a freshwater acquarium (30 gal) that i had fish in for many years without the need to treat for chlorine.
 
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Just a thought, rocks from a quarry often have undesirable chemicals on them. For example, one that often contaminates water sources from blasting is Perchlorate. If it or any of the other residuals from blasting are present that could be why the fish died. Rapid ph change is of course another killer.
 
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It could very well be caused by the rocks in the pond. I could experiment with removing all the rocks in the pond to see what happens. If there is no water degradation/ph spikes we'll know the culprit and I can take steps to clean the rocks.

Thanks, and if anyone else has anything else, please feel free to chime in.
 

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When I bought my rocks at our concrete place I took them home and hosed them all off in the driveway and left them out there through some rains also just to make sure they were rinsed off good. Maybe you will have to drain the pond and hose off the rocks in there and drain and try to make sure they are rinsed good. Would be way to hard to remove them all now.
 
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Thank you. I certainly cannot remove the cemented in rocks, but there are many loose rocks inside the pond sitting on the surface.
I will try and do that this weekend and let you guys know my result. I may blast them with muriatic acid.
 
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Thanks for your replies. I doubt it's ammonia, and for your information the pond is 500 gallons and the most recent batch of fish were added after a near complete water change.

It could very well be the rocks in the pond, they are not specifically pond safe and are blasted rock which were obtained by my stone mason.

There is no algae in the water.
You should wait a few weeks before adding fish after the water change.
 
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You should wait a few weeks before adding fish after the water change.

Yes, this would be the prudent thing to do to get the biology correct in the water, however, it does NOT explain a PH spike from 7.5 to 9+ in 24 hours (and worse now). Yes, a small variation would be understandable.

My stonemason is inquiring with the pond paint company about curing. It may need more time for curing....

Thank you.
 
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No, can you tell me more?
I'm guessing the test is to determine whether the rocks has a high component of limestone.
As for my fish comment, I didn't imply it was causing the spike, but there's no reason to continue adding fish till you get the water quality figured out. Hope you get this figured out soon.
 
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This may be an annoying solution but I would suggest doing 3-4 total water changes and see the PH a day after the last water change. If the ph rises after the last water change then you have a substance leak problem for sure.
 
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