Buffering Kh?

[thecommonnate]

bump

to nmonks, I'm still trying to figure out KH, and the above was the only thing I didn't understand about your explanation.

 

[nmonks]

The end product of the nitrogen cycle in a filter is nitric acid, rather than nitrate. Carbonate hardness buffers this, producing the nitrate. There's a detailed summary over at The Krib. But the main thing is that as nitrate goes up, carbonate hardness goes down, and so the tendency for pH to drop becomes steadily more serious.

Cheers, Neale

 

[Bignose]

But most other habitats* are extremely stable: Rift Valley lakes, major rivers, coral reefs for example. Fish from such places won't be experiencing significant pH changes across a daily cycle. I find it inconceivable such fish could adjust to 4 units -- pH 5 to pH 9 -- within an hour!

Neale, I found it incredible too when I first read it. Nevertheless the scientific literature is very clear about how well fish respond to pH changes. Please don't just take my word for it, read the sources I cite in those posts. That change of 4 pH units is actually exceptionally conservative -- I took a flux rate that was 10% of the measured flux rate to keep the number very conservative.

There is much other corroborating evidence in the scientific literature. A healthy fish with the correct minerals available in the water can adjust to pH changes very rapidly.

 

[nmonks]

It's not that I don't believe this may well be true under lab conditions, or that many fish in the wild can tolerate quick changes in water chemistry without undue harm. But I think it's a misleading factoid when used in fishkeeping.

For a start, fish adapted to high pH levels quite clearly have little to no tolerance of acidic water. Try changing the pH of a Malawi, Tanganyikan, brackish water or marine aquarium from 8 to 6 and you'll get a lot of dead fish whether you do it quickly or slowly! Conversely, fish adapted to very soft water habitats such as rams, wild discus and Hemirhamphodon halfbeaks are used to water that contains few bacteria; keep them in hard water tanks with a high pH and they're much more prone to infections. Other pH-related issues include the toxicity of ammonia and nitrite at varying pH levels, and the decreasing effectiveness of biological filtration at acidic pH levels.

So there are plenty of practical reasons why a particular pH will be optimal for a given aquarium.

The key thing is that pH, hardness and carbonate hardness all go together. Too many aquarists focus on just one thing, usually pH, without understanding that the other two aspects of water chemistry need to be considered and perhaps altered accordingly. Hence my argument that if you don't understand all three aspects, don't change any of them; and if you're going to change one of them, then you will probably need to adjust or at least monitor the others too.

Cheers, Neale

 

[thecommonnate]

thanks!