off topic FW low ph

[beaslbob]

All:

On another forum I'm getting some grief (which happens).

A poster started a 15g tank with 6 neon tetras and 6 orange tetras. The neons died in 5 days and the oranges were dying off one by one. Ph was 6.5, ammonia 0, some nitrates.

My post was that the 6.5 pH indicated high carbon dioxide so possible the fish were suffocating. Add live plants to suck out the co2 which will raise the pH. (and also suck out any ammonia as well).

For this I got a lot of negative reactions.

To me obviously they set off a cycle and high co2 could have been one side effect.

So what think you.

 

[Randy Holmes-Farley Verified Community Expert]

pH in freshwater can be controlled by different buffers than in marine systems. For example, phosphate buffer. But higher CO2 certainly always lowers pH. But pH 6.5 does not necessarily mean high CO2 if the alkalinity is low. If the alk is 1.5 dKH, and the pH is 6.5, the CO2 is actually low according to a table in the freshwater article below:

https://www.practicalfishkeeping.co.uk/features/articles/co2-striking-the-balance

 

[beaslbob]

thanks.

 

[beaslbob]

using that chart kh was 40 (ppm) ph 6.5 resulted in a safe co2 of ~20. In my tanks kh=4 degrees pH is 8.4+ for less than 1.2 ppm.