Stubborn KH

Tman · Post by **Tman** » Fri Sep 22, 2006 6:18 pm

I am trying to increase my Kh to 50 pmm (3dkh) from 0. I have increased the Kh to 3dkh and Ph around 6.6 but it always come back to 2 dkh and ph around 6.4. I have tried this for the third time now and its still the same result.

Anyone experienced this before?

ToddnBecka · Post by **ToddnBecka** » Fri Sep 22, 2006 9:10 pm

Are you trying to raise the pH as well, or just the KH?

Post by **Mustafa** » Fri Sep 22, 2006 11:02 pm

Why on earth would you want to increase the ph by 0.2? There is really not much difference for any acid water shrimp species between 6.4 and 6.6 ph. Your kh keep going down because nitric acid and other naturally occuring acids in your fish tank keep eating away at your kh.

Todd...kh and ph are interdependant...you might want to read up on general aquarium water chemistry a bit. Nobody should try to maintain a certain kh as it's erroneously recommended in many websites. You only add carbonates or acid to change the ph to a desired value and the kh is automatically affected by it. For me kh is totally useless and I never measure it.

ToddnBecka · Post by **ToddnBecka** » Sat Sep 23, 2006 12:23 am

The higher the KH, the more stable the pH will remain. You can use baking soda to raise KH, and the pH will "rebound" until the buffer is broken. It can be frustrating to try to adjust water parameters.

badflash · Post by **badflash** » Sat Sep 23, 2006 5:59 am

Fighting the water is useless and unless there is a compelling reason, just don't do it. You need to find the source of the acid. Your pH is fine for now.

If your pH is crashing down into the 5's or 4's you have stuff decomposing and making acid. I experienced that with my sand substrate that got choked with waste. Changing this out for larger gravel fixed this issue.

Post by **Mustafa** » Sun Sep 24, 2006 9:59 am

ToddnBecka wrote:The higher the KH, the more stable the pH will remain. You can use baking soda to raise KH, and the pH will "rebound" until the buffer is broken. It can be frustrating to try to adjust water parameters.

That is a myth, especially when it comes to acid water animals. Fact is that your ph goes up automatically if you try to increase your kh for "stability" by adding baking soda. There are people out there who ignorantly recommend all kinds of kh values, usually 3-4 kh, without realizing this. If you want alkaline water then you can add baking soda (bicarbonate) or other alkalinity builders...but it's definitely *not* for stability. In the above case, where someone is obviously trying to keep acid water shrimp, trying to raise kh for "stability" is utter nonsense as adding bicarbonates will just dramatically increase your ph and counteract what you are trying to achieve. I've said it many times before....kh as a measurement in aquaria is absolutely useless. Stick with ph and conductivity measurements and you'll be fine.

ToddnBecka · Post by **ToddnBecka** » Sun Sep 24, 2006 11:32 am

It is a fact that baking soda will raise kH, along with pH to a max of 8.2-8.4. After that pH is reached, more baking soda will raise only the kH.
I tried to raise/buffer pH in an aquarium with baking soda years ago, and found that it kept dropping (rebounding to the original value) within 24 hours. Someone told me that the water chemistry has to reach a point where the buffer is neutral to raise or lower pH.
I know from experience with keeping African Rift Lake cichlids that baking soda will raise kH as I stated, and that higher kH levels make the pH more stable.
The problem I was trying to combat years ago, by raising/stabilizing the pH, was "old tank syndrome". An aquarium that has been running for a couple of years tends to become acidic, due to biological activity. The trouble in general is that water either tends to be hard and alkaline, or soft and acidic. The acidic water "eats" kH, as do live plants, that use the carbon aspect of carbonate hardness.