High Ph In Pond

[RossC]

I water tested my pond water today and found everything was 0ppm but the pH was at 8.4! Now my tapwater is around 7.4 and I'm not using any buffers and as far as I'm aware there isn't anything such as rocks that could adjust the pH so much, its got a thin gravel substrate. I have noticed the water is pretty green and algae is thick in places. Could the pH rise be due to algal activity?
Its filtered using plants and a circulation pump that blows through a bag of ceramic rings. I have added an air powered sponge filter to give a little extra filtration. Any ideas or suggestions would be appreciated. I also did a 50% water change today after the tests were done.
Thanks

 

[Brilly91]

is the pond ground level? or raised? seen water run off cause issues with ph before.

 

[mark4785]

I water tested my pond water today and found everything was 0ppm but the pH was at 8.4! Now my tapwater is around 7.4 and I'm not using any buffers and as far as I'm aware there isn't anything such as rocks that could adjust the pH so much, its got a thin gravel substrate. I have noticed the water is pretty green and algae is thick in places. Could the pH rise be due to algal activity?
Its filtered using plants and a circulation pump that blows through a bag of ceramic rings. I have added an air powered sponge filter to give a little extra filtration. Any ideas or suggestions would be appreciated. I also did a 50% water change today after the tests were done.
Thanks

 
Bad algal blooms use up a lot of co2 to grow during the day which causes the algae to release a lot of dissolved oxygen. Dissolved oxygen is alkaline and therefore pushes the PH up.
 
I recommend you try to get the algae under control by installing an abundance of wool in your filtration unit as this is excellent at removing green water algae spores. Blanket weed may also be contributing to your PH rise. This, from years of experience, can only be removed physically so I recommend getting an efficient pond hoover like the Blagdon Pond Monster to remove it. To prevent blanket weed and green water be sure to install wool in your filtration unit and use barley straw pouches all year round to naturally prevent algae from growing.
 
Be sure to test your water's KH. If it is below 4 dH, I recommend you up it to 6-7 dH as this is your natural buffer against drastic PH swings. Biological activity and algae problems are known to use up the buffer quite quickly; if your buffer is below 4 dH you run the risk of a PH crash which is capable of killing fish.

 

[RossC]

Bad algal blooms use up a lot of co2 to grow during the day which causes the algae to release a lot of dissolved oxygen. Dissolved oxygen is alkaline and therefore pushes the PH up.
 
I recommend you try to get the algae under control by installing an abundance of wool in your filtration unit as this is excellent at removing green water algae spores. Blanket weed may also be contributing to your PH rise. This, from years of experience, can only be removed physically so I recommend getting an efficient pond hoover like the Blagdon Pond Monster to remove it. To prevent blanket weed and green water be sure to install wool in your filtration unit and use barley straw pouches all year round to naturally prevent algae from growing.
 
Be sure to test your water's KH. If it is below 4 dH, I recommend you up it to 6-7 dH as this is your natural buffer against drastic PH swings. Biological activity and algae problems are known to use up the buffer quite quickly; if your buffer is below 4 dH you run the risk of a PH crash which is capable of killing fish.

Ok thanks, I'll look into some of the methods you've provided, appreciate the help
 

is the pond ground level? or raised? seen water run off cause issues with ph before.

It is above ground, with a bank of gravel around it so run off is very unlikely but thanks for replying

 

[MBOU]

So long as its stable at 8.4, its fine, don't mess with it! (though checking hardness is an idea too). Its when ponds top up with rainwater and it drops the ph to 6 or so that its a problem.

 

[RossC]

Although I haven't actually tested my pH I did install a new filter and the algae has got a load better, the water is almost crystal and the fish are more active so it seems to have fixed it but I suppose only an actual pH test will tell