Originally Posted by matthewburk
Hmm so you are saying if fish like acidic water what is really meant by that is low KH. Is it really that simple, becuase if that is the case why don't the resources just say that? You've really got me confused right now, like I shouldn't care about PH at all. Do cichlids like high KH, not high PH, meaning I could bring the KH up with baking soda and inject co2 bing the PH down to around 7 without any health risks to the fish?
That is my understanding. Fish like either hard or soft water in terms of GH and KH. However, try to inject co2 into a tank with a KH of 15d (270ppm), and you wont notice a huge change in pH levels. The lower the KH the more drastic of pH changes you will see, and vice versa. So even if in an extremely hard tank you dose co2, you may very likely still have a high pH even at co2 of 30ppm.
saying "shouldn't care about pH at all" may not be the right wording, but when you think about it pH is just a formula when it comes down to it. Just the offset of KH by how much acid content is in the water. pH = 7 - log[acids in ppm / (3*dKH)]. I have heard pH after acidic injections called "artificial pH", which pretty much sums it up. If you were to insert 3ppm into the 'acids in ppm' part of the formula, you will get to what your natural pH levels are: 7 - log(1/dKH). That is if you had no acids (3ppm co2 is in our atmospheric levels, so that is a minimum constant).
Another point is that in my 180g tank with a Sting Ray in it, I keep my KH at 1d (18ppm), which equates to 7.0 pH (naturally neutral). They like "very soft water". The nitrogen cycle plays a part in reducing the KH in the water over time, so I see massive drops in pH quickly, unless I do a daily dosing of Baking Soda to keep the KH as consistent as possible. IF I forget, which go figure does happen, my KH will drop to .25dKH in no time, causing my pH to drop below 6.0. I have seen it even be 5.3 before (and maybe less). *This is not safe to do, so in no way am I recommending this*.
In my situation, if you were to even do a 25% water change with 2dKH tap water (what I have), the KH level will jump up to near 1dKH again, which means the pH will automatically jump up to 7.0 again. Thus, there have been immediate changes of 1.7pH in my tank on many many many occasions. 5.3 to 7.0. Did the fish mind it? No. Why? Because there was only a small change in KH. The actual pH didn't matter. And Sting Rays are extremely sensitive to water conditions!
Where pH matters is in cycling tanks. I forget which way it works, but in one of high or low pH conditions, ammonia is more deadly to fish. For all I know, that may still be just a factor of ammonia being more or less sensitive when acids are present, &/or maybe KH plays a part in healing fish from ammonia effects... not sure myself, but maybe it is pH that matters in that situation.