I read here That my low KH (its 3dH from the tap and i tested 2dH in the tank after a 50% water change) can make the Nitrates more of a burden on pH. So basically, I need to increase the KH so I can have a better buffer against the nitric acid from the Nitrates.




THis is the information provided on the above reference site.

"Adding sodium bicarbonate (baking soda). One teaspoon of baking soda added to 50 liters of water can raise the kH of the water by approx 4dH without a major affect on pH."

I have a 20 gallon tank which is roughly 75 liters. So adding 1.5 teaspoons of baking soda to the tank should raise my KH to between 6 & 7dh.

Does the baking soda stay in the tank the way salt does? Do i need to make sure that after the initial dosing of baking soda, that I only add more based on the water change amount? Or does it disappear or get used up over time? Does anyone have any experience with adding a buffer to the tank?

Hi Goldphishe,

The chemical reaction for the conversion of ammonia to nitrate is:

NH4 (ammonia) + 2 O2 (oxygen) --> NO3 (nitrate) + 10 H (hydrogen ion) + H2O

So you can see that for every molecule of ammonia that is converted to nitrate, you get 10 hydrogen ions. pH is a measure of the hydrogen ions in the water. That is, pH decreases as the hydrogen ion concentration increases. This is the reason why pH is falling as nitrate increases in a poorly buffered system.

When you add baking soda (NaHCO3) to the tank it separates into sodium and bicarbonate ions. The sodium remains in the water until removed by water changes. The bicarbonate (HCO3) will equilibrate with other inorganic carbon compounds including CO2. This means that some bicarbonate may exit the tank as CO2 or precipitate as calcium carbonate. At neutral pH, this will occur very slowly so you only need to add baking soda with every water change.

wow, it's a very good explanation!!! Good job Kingyo...

since the sodium stays in the tank until a water change, and since I wouldn't do a 100% water change, do I still add the full 1 1/2 tsp of baking soda to the water (to dose the entire tank) at every water change?

I don't know how much Baking Soda you have to add back to the tank. But I am sure you have to add back. I have to put 1/2 teaspoon to my 29 g tank whenever I change water.

Just add it proportional to the water change. If you do a 30% water change, add 0.5 tsp.

whats the difference between adding Baking Soda or a commercially availibe buffering product (aside from price)? I was looking online and found Seachem Gold Buffer which was later recomended to me by my LFS.

Baking Soda is cheaper than the others for the same job

commercial buffers are more expensive. However, many of these will have a combination of bicarbonate and carbonate salt to buffer at the right pH. In addition, their mixture may have less sodium than baking soda.

another important thing to remember is that buffers can get used up over time. You need to monitor them. and the buffers in tap water tend to flucuate. Using baking soda should not lull you into believing that everything will be fine from there on. You still need to test regularly.