To some extent my comments were sarcasm, I apologize for that. The person who questioned the info did so by saying they would stop buying all kits that their fish were unable to read. I responded more harshly than I probably should have.
I do own Ph test kits, and do use them, but seldom worry about what my PH actually is or how much different tank and tap Ph really are. The fish react to the level of dissolved solids, not the actual ph of the water. PH "shock" as it is commonly called in the hobby is actually Osmotic shock caused by taking a fish from water with one TDS (total dissolved solids) level, and putting them in water with a far different level. This interferes with osmo-regulation and harms the fish (or in mild cases stresses the fish) fish can and will adjust to changes, but it takes some time. My tanks range from 6.6-7.2 Ph with co2 injection, my solids levels and Carbonate levels are constant and consistant with my change water. the fish don't know the difference in the ph.
All of this is of course within the ranges of normal Ph's. Extreme high's and lows will still do harm, but seldom does this discussion ever contain the extremes. I have seen tanks with OTS that regularly tested at ph of 5 and the fish survived. and likewise I have seen fish kept in tanks with ph of 8.8 with no problems.
That being said, the Ph myth is huge and largely mis-understood.
It comes from the fact that what we as humans view as hard water is far different than hard water in the sense that fish care about.
Human hard water is water that is hard to get soap suds in, for fish it is water that is high in TDS (total dissolved solids). A person can take RO water and adjust it to a Ph of 8.2 and have less dissolved solids than high calcium water would have at a ph of 7.0. The Ph correllation is extremely general and far too much emphasis is put on it. Here in Columbus Ohio we have tap water that is pathetically devoid of everything. Our water comes from the pipe at close to 7.0 ph most of the year. it changes to 7.6-7.8 after sitting out for a while. Now the crux of the matter is: there isn't enough calcium, magnesium, trace minerals etc. in that water to grow plants, snails, or shrimp. By all rights our tap water at 7.8 ph is nearly perfect for ultra soft water fish like tetra's and discus. Mollies and swordtails will not breed in our tap water because it is so soft. on the flip side I can take that same water and make it rock hord with calcium and magnesium and never alter the ph one iota. Then I have water ideal for rift lake fish, mollies, snails, shrimp etc. and the ph is still exactly 7.8.
A water softener exchanges calcium and magnesium ions for sodium ions at close to a 2 to 1 ratio. In other words the water going in is high GH, we double (general term not mathmatically accurate) the dissolved solids, and it comes out reading a lower GH. Discus would rather have the water before it was "softened"
Now thus far we have talked about calcium and magnesium, and of course carbonate. Our GH test kit picks up an Ca and Mg, but does not read other items in the water. Our Kh test kit picks up on Carbonate, but does not read other factors. So we could feasably have high iron, high sodium, high sulfur etc etc. And our test kits read ultra soft water. Dump a discus in a high sodium high sulfer tank sometime (please don't do that for real) and you'll find out ph Kh and GH readings mean next to nothing in the total picture.
Likewise we could take ro water add enoguh calcium and magnesium, to get a gh of 18-19 dGH and just enough carbonate to get a KH of 3dKH and we would have a ph of 7.8 or 8.0, Medium hardness reading, medium to low Kh and high Ph. With nothing else in the water, our fish would still see it as very soft water.
There are so many variables in the PH discussion, and so many right and wrong ways to influence Ph that in the end it proves to be a somewhat useless number. It is good for viewing changes, it is excellent for calculating co2 levels (if carbonate is the buffer and not phosphate) but aside from that it is limited in what it will actually tell us. Additionally because of the emphasis put on PH readings by so many people in the hobby, it causes a lot of confusion, a lot of headaches, and in many cases it kills a lot of fish.
In the wild, the water works under different rules, we have large volumes of water with small numbers of fish. A KH of 0 in the wild is not a big issue because there is enough water to dillute the effects of biological acidification a KH of 0 in our tanks is a recipe for dissaster. Many People constantly work for a PH of 7.0, when in fact they are setting themselves up for an unstable tank environment when they do that. Our tap water at 2-3 dKH is Ph of 7.6 at atmospheric co2 levels. This tells me that unless I'm injecting co2 I never ever want a tank with a PH below 7.6 PH.
When we use products like peat the tannic acid depletes the carbonate, the calcium and the magnesium (at least that is my understanding at this point) this is a good and useful thing to know if we have extremely hard water and we want to raise Discus fish. It is not a good thing if we don't understand the whole picture and we over soften our water and crash the tank.
Trying to get the entire aquarium hobby to see this is difficult at best.
We need an article! A sticky! I was JUST looking for that recent thread where Dave is explaining why pH isn't as important as most people think.
I had actually already started putting this information to paper, but It will take some extensive time to get a good article posted. I do not want to throw theories only onto the boards, I am currently trying to buy a TDS meter, after which I will get some RO water, and variuos well water and tap water samples, and do some proper testing to produce real numbers to back up my claims. Until I get that done, I'm sure there will be a lot of questioning (always a good thing) and some argument to this whole subject.
The bottom line for quick reference is:
GH test reads calcium and magnesium only
KH test reads corbonate which is IMO and IME the only dependable buffer
PH reads how acidic or basic the water may be with reasonablyclose correllation to Kh and very very loose or general correlation to GH.
Phosphates buffer water, but are unstable and short term at best
Co2 drive Ph down without drastically changing Kh, and the correllation is very close.
Peat, driftwood, extracts etc. will truly soften the water, they are slow to act in well buffered tanks and will rapidly drop the ph in a tank once Kh is depleted. These items should be used with caution and understanding.
Most other solids in the water cannot be tested for with normal hobbyists kits. Iron tests are arguably unreliable, as with many less popular test kits. the ideal thing to do is get a printout of the local utilities water test results.
And of course the easiest tank to maintain is one that has water identical to tap. frequent steady water changes will keep everything regulated stable and healthy unless your tap water is really extreme in some regard. Fish will easily adjust to most levels of Ph, Kh and GH within reason.
Dave
), but I don't worry about my pH nearly as much as my kH. The kH keeps the pH stable (important), most of my fish adapt to a wide range of pH values (so why worry about what it is?). If you want to know your pH out of tap/tank/etc, you could always take a sample to the LFS and find out what it is.
