Low PH mystery solved!

javajo

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OK - here's the scoop.

I went about my water change as usual last Sunday. Prior to the change, my PH was once again down to 6.0 or less. My KH was 1dkh.

After my 7 gallon change (29 gl tank), my ph was back up to 6.4 (approx.) My KH was still at 1dkh.

Then I tested the KH of my tap water - 2dkh!

That explains allot! This is probably the main reason why my PH is so low, and so unstable!

Aftrerwards, I added 1 tsp of baking soda. Whoa!..what a difference!

My KH shot up from 1 to 3dkh and my ph shot from 6.4 to 7.0.

I was a bit worried about the ph spike and the safety of my fish but knock on wood they're doing fine. To play it safe I added 6 tsps of Stress Coat to the tank. I normally do this anyway after a water change.

On a side note, my WaterSprite and Cabomba are continuing to grow like weeds - especially the Cabomba!

My Ludwigia appears to be doing fine, just growing at an average pace.

Why would the 2 degree increase in my KH raise my PH so quickly? I understood KH to be a measure of the stability/alkaline content of the water. I was expecting my PH to simply become more stable and through water changes, steadily raise myPH.
 
That's good news, javajo, but it still seems, from what I understand, that your pH should probably be a little higher (around 7.3-7.4 with a KH of 3 deg). It could be that you still have some pH lowering substances in there, but if it stays a stable 7.0-ish, personally I wouldn't worry about it too much.

Why would the 2 degree increase in my KH raise my PH so quickly?

From my understanding, the extra carbonates will provide molecules that the hydrogen ions will readily bond with. So, you have, statistically, less H+ ions in the water, and therefore the pH rises. The quickness (I'm guessing you tested a half hour or so after adding the baking soda?) doesn't seem odd to me, but that's mostly just a "hunch" on my part.
 
Thanks Bol -


('m guessing you tested a half hour or so after adding the baking soda?)

Actually, I didn't even wait that long - more like ten minutes after adding the baking soda I tested the water.

Just tested the water yesterday. Added baking soda last Saturday or Sunday. PH still at 7.0 .... KH down from 3 to 2 dKH.

Might need to get the KH a bit higher so it's more stable.
 

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