pH In A Pond

[SeaWitch]

I live on the East coast and we have the softest water in the U.S. I have to buffer my water in my aquarium at every water change. The pH from my tap varies from 6.4 to 7.2.
However, I have noticed that in my pond, the pH is very high and is stable. I never have to buffer the pond at all. My pH out there stays above 8.0. Can someone please explain to me why this happens in a pond setting?:youtellme: I'm just curious.

[Sabine]

I observe the same thing - it's the algae that cause the high pH.

[bekko]

Check you pH at dawn and get a surprise !! When the sun comes up and photosynthesis kicks in the algae start sucking up the carbon dioxide. Since carbon dioxide is a weak acid the pH increases as it is removed for photosynthesis. During the night, carbon dioxide is replenished from the atmosphere and from algae respiration so the pH falls again.

We all know that a stable pH is better than a fluctuating pH. However, these diurnal pH fluctuations caused by algae do not seem to do any harm. I cannot explain that one.

-steve

[BruceP]

Adding baking soda helps to stablize the ph and raises the KH , a good thing as your filters use kh and more is better. The natural PH of baking soda is 8.3 so it wont raise the PH tooooo much. Having said that, I'd probably do nothing if it stays consistantly at 8.. :)

[SeaWitch]

Well now I am confused! If I use the baking soda to buffer it, will the algae increase that pH even more during the day? However, now I am scared of that drop that happens at night! My fish seem fine, so, as Steve stated, the pH drop does not seem to be bothering them. I guess there is really no way to have a constant pH in a pond setting if you have algae, is there? The algae will constantly raise and lower the pH.

[bekko]

Adding buffer never hurts. If your water is really soft it could be dropping to sixish at night.

-steve

[goldencarp]

Does the algae issue have anything to do with why, after a rain, my fish all seem to be gulping for air at the top of all my ponds?

[SeaWitch]

It could be. What type of filtration do you have?

[bekko]

The rain water is cooler than the pond water so it sinks to the bottom. This displaces water at the bottom lifting it up into the water column. If there is a lot of loose debris on the bottom the water within that debris may be devoid of oxygen. When it's really bad, the water at the bottom can actually have an oxygen deficit (it is essentially less than zero). When this bottom water if lifted up it can cause the oxygen concentration in the entire pond to drop. Fish farmers call this phenomena a "turn-over" and it can be deadly. Do you have adequate aeration and does the bottom of your pond need to be cleaned?

-steve