Hardness Clarification

[PeteCW]

OK, so I have kept and successfully maintained fish and aquatic plants for about a year now, and I (think) I have read just about everything the net has to offer about freshwater aquarium management, but there is one remaining issue which still seems ambiguous or undefined- the actual effects of carbonate hardness and general hardness on fish.
Now I'm a chemist by profession, but the info I have been reading on the net, and also in a few books, seems to be conflicting and points toward a mass misunderstanding, but then again, I have been known to be mistaken :o
The problem is, when a website or book attempts to list a summary of ideal chemical water parameters for a particular species of fish, some sites will only specify a kH value, others will specify only a gH value, and on occasion I will come across a site that provides some vague "hardness" value that they call "dH"?! Well obviously they mean "deutsch hardness", but that doesn't exactly help much...other than you multiply the number by 17.9 to get a value in accordance with IUPAC standard nomenclature.
So let's get down to brass tacks...
kH= carbonate hardness (amount of CO3 2- anion in solution) or "buffering capacity", meaning the ability of the water to resist a change in pH due to other chemical influences.
gH= the amount of total +2 cations (magnesium, calcium, and in much smaller quantities, beryllium, strontium, and barium) dissolved in a given volume of water.
dH= unspecified? God only knows.
TDS (total dissolved solids)= the total amount of all disolved minerals, including sodium, calcium, magnesium, and all the rest. In fact, many common test methods for salinity actually measure the TDS.
So with this established, lets get to my assumptions about how these parameters will affect fish...
kH- Particularly in a planted tank, depending on the kH, there will be a less or greater drop and rise of pH during the day-night-day cycle. This is all I can think of. Are certain species of fish really that sensitive to such a temporary fluxuation?
gH- I can clearly see how this would affect the osmotic pressure of the water and have a significant effect on gill function, and to a lesser extent on internal/external body pressure differential (water depth and swimming level would have a greater effect, but not in the average fish tank).
TDS- this effect would be comparable to gH, though this introduces the additional affect of the possibly abundant Na+ (sodium) cation on the fishes biochemistry.
Therefore, my general concern lies in the lack of consistant and/or explanatory information (or archaic nomenclature) from all the various aquarium websites out there.
Does extreme fluxuation of pH bother some fish more than others to a significant extent?...or does the osmotic pressure of the water aggrivate them more?...or is it a combination of both? As for the effect of dissolved sodium on certain species (cory's; tetra's) is understandable and somewhat clearly documented, I'm not concerned with that, but for instance, if you go to Foster&Smith's website, all they talk about is kH, but interestingly, when they reference plants, they only reference gH. On the other had, if you go to the Eheim Fish Database, they are solely concerned with gH.
I ask you, is this merely uninformed and oblivious misunderstanding, or are both parameters significant for freshwater fish, or are some parties informed and others not quite clear, or is there something vital I have missed altogether???

[PeteCW]

I'm sorry to have replied to my own post but, is this really that much of a casual (layman's) forum?
Perhaps I was mistaken and should go elsewhere...like the apparently infamous graphicdesign_r...I don't know (never read this person's posts)!
It's in your hands now.

[daveedka]

First let me say that the problem you are viewing is due to a huge myth/ misunderstanding in this hobby. Natural waterways typically contain the +2 ions you refer to and natural water usually gets those ions via CaCo3 and MgCo3 and therefore in most natural water, The Kh/pH/GH are all Somewhat in correlation. In other words many people fall into the myth that pH is somehow an indicator of General Hardness. Municiple water treatment of course negates any GH/ pH correlation or at least the ability to depend on one. To some extent municiple water treatment can negate the pH/KH correllation as well, and additional confusion is added by forced Co2 levels in piping, and the fact that many people do not allow time for gas exchange before testing their tap pH

Fish are not highly sensative to pH, I am not convinced they are sensative at all. Fish are sensative to changes in TDS levels and therefore since most people do not seperate or understand the different test reading, they confuse the effect of TDS's with the percieved effect of pH.


KH is as you described but becomes very significant in our tanks because the biological processes of our bacteria consume KH. In a closed system the processes are much more significant because of the high biological activity per gallon. If tap water Kh is low to begin with, or a good maintenance routine is not kept then KH will be depleted over time and the pH will crash in the tank. Additionally the Bacteria will die off in 0 KH low pH environment. When the bacteria are killed, the tank will essentially need to be re-cycled. Plant keepers who inject Co2 additionally need the stability of adequate KH levels to control the effects of the carbonic acid produced when increasing Co2 levels in the tank.


GH is also as you described, but our typical hobbyists tests only pick up on Ca++ and Mg++, so the other ions do not really come into play on testing numbers unless we have lab grade testing ability, and even then most if not all standards are written based on hobbyists kits so the lab grade tests would do little more than indentify possible variations in your specific water supply.

TDS is the true measure of what is in the water, and is also the true issue with how fish react to that water. "Soft water" fish like low TDS levels, and "Hard Water" fish like high TDS levels. As you mentioned, TDS levels lend heavily to the process of Osmoregulation, and rapid changes in TDS will "shock" a fish. The term pH shock is a misnomer, it would be much better termed "Osmotic Shock"
For the most part fish are adaptable anyhow, given decent acclimatin time. but if we wanted to create specific environments for breeding or other purposes, then TDS levels would in reality be the way to test. In addition to the issue of captive breeding, some extremely sensative fish will show better colors when not presented with specific ions in the water. In other words, Some fish react specifically to the Mg++ and Ca++ (Or other ions) and that becomes the issue as much as the TDS levels in general.


DH is most likely someones attempt at confsuing an issue that already has enough mis-information, and is probably stated by someone who is close to clueless on what is really effecting their fish. I have not yet seen any Test kit Literature that defines DH, I of course have not read all of the literature out there, but no one I've talked to who really understood the hardness issue has ever used the designation, it typically shows up on the forum boards, or in abviously mis-guided articles.

With modern municiple water treatment and the ease of obaining RO and DI water, people who understand these parrameters can manipulate for a wide variety of practices without a lot of work, a degree in chemistry, or a lot of cost. Additionally people who ignore the pH myth and focus on KH for stability and other needed ions for their specific tanks will be able to create ideal environments for teir plants, and invertibrates. Fish don't care for the most part as long as they are presented with a clean, stable environment they will be happy in all but smallest percentage of situations.

dGH and dKH respectively are Degrees of general Hardness, and degrees of Carbonate hardness. Many test kits are still calibrated in degrees rather than ppm (mg/L) so it's good to know the conversion and also necessary to know how your kit is calibrated. 17.9 ppm to a degree for both GH and KH.

Lastly, Graphicdesigner was a troublemaker who continued to bring up problematic subjects that had nothing to do with exchanging valid information, or helping people with real questions. He did this at times when the Boards were experienceing multiple other problems as well, and he continued to do so despite warning that action against him would be taken. I for one do not understand folks who come here just to make life difficult for the mods, and Additionally don't appreciate the B.S. That folks like Graphicdesigner cause. Most of the active long term and knowledgable members (And some of the rest of us) have moved on to greener pastures because of those situations. If Graphicdesigner is gone, I say good riddance, but then I don't really care because I too have moved on to a much better forum and only stop in here once in a while to see how things are going.

dave

[PeteCW]

Thankyou for replying Daveedka with your perspective on this issue, as you more or less confirmed my assumptions and suspicions, though I kind of knew that would end up being the case if any one who vaguely had any kind of true understanding would confirm.
There are a couple of finer points that you mentioned that perhaps I could shed a little clearer light on, for the benefit of all, but what do you say we save that for aquariumboard.com...