Dumb question/ What is KH and GH

[Dubiadiscus]

I just bought a freshwater master test kit. I didnt seen anything in there to test the KH and GH, or does these two stand for somthing else or do i have to buy a seperate test for GH and KH.
Thnks for the help and info

[seanyuki]

Just sharing.....


pH
pH refers to water being either an acid, base, or neither (neutral). A pH of 7 is said to be neutral, a pH below 7 is ``acidic'' and a pH above 7 is ``basic'' or ``alkaline''. Like the Richter scale used to measure earthquakes, the pH scale is logarithmic. A pH of 5.5 is 10 times more acidic than water at a pH of 6.5. Thus, changing the pH by a small amount (suddenly) is more of a chemical change (and more stressful to fish!) than might first appear.

To a fishkeeper, two aspects of pH are important. First, rapid changes in pH are stressful to fish and should be avoided. Changing the pH by more than .3 units per day is known to stress fish. Thus, you want the pH of your tank to remain constant and stable over the long haul. Second, fish have adapted to thrive in a (sometimes narrow) pH range. You want to be sure that your tank's pH matches the specific requirements of the fish you are keeping.

Most fish can adjust to a pH somewhat outside of their optimal range. If your water's pH is naturally within the range of 6.5 to 7.5, you will be able to keep most species of fish without any problems. If your pH lies within this range, there is probably no need to adjust it upward or downward.
Buffering Capacity (KH, Alkalinity)
Buffering capacity refers to water's ability to keep the pH stable as acids or bases are added. pH and buffering capacity are intertwined with one another; although one might think that adding equal volumes of an acid and neutral water would result in a pH halfway in between, this rarely happens in practice. If the water has sufficient buffering capacity, the buffering capacity can absorb and neutralize the added acid without significantly changing the pH. Conceptually, a buffer acts somewhat like a large sponge. As more acid is added, the ``sponge'' absorbs the acid without changing the pH much. The ``sponge's'' capacity is limited however; once the buffering capacity is used up, the pH changes more rapidly as acids are added.

Buffering has both positive and negative consequences. On the plus side, the nitrogen cycle produces nitric acid (nitrate). Without buffering, your tank's pH would drop over time (a bad thing). With sufficient buffering, the pH stays stable (a good thing). On the negative side, hard tap water often almost always has a large buffering capacity. If the pH of the water is too high for your fish, the buffering capacity makes it difficult to lower the pH to a more appropriate value. Naive attempts to change the pH of water usually fail because buffering effects are ignored.

In freshwater aquariums, most of water's buffering capacity is due to carbonates and bicarbonates. Thus, the terms ``carbonate hardness'' (KH), ``alkalinity'' and ``buffering capacity'' are used interchangeably. Although technically not the same things, they are equivalent in practice in the context of fishkeeping. Note: the term ``alkalinity'' should not be confused with the term ``alkaline''. Alkalinity refers to buffering, while alkaline refers to a solution that is a base (i.e., pH > 7).

How much buffering does your tank need? Most aquarium buffering capacity test kits actually measure KH. The larger the KH, the more resistant to pH changes your water will be. A tank's KH should be high enough to prevent large pH swings in your tank over time. If your KH is below roughly 4.5 dH, you should pay special attention to your tank's pH (e.g, test weekly, until you get a feel for how stable the pH is). This is ESPECIALLY important if you neglect to do frequent partial water changes. In particular, the nitrogen cycle creates a tendency for an established tank's pH to decrease over time. The exact amount of pH change depends on the quantity and rate of nitrates produced, as well as the KH. If your pH drops more than roughly two tenths of a point over a month, you should consider increasing the KH or performing partial water changes more frequently. KH doesn't affect fish directly, so there is no need to match fish species to a particular KH.

Note: it is not a good idea to use distilled water in your tank. By definition, distilled water has essentially no KH. That means that adding even a little bit of acid will change the pH significantly (stressing fish). Because of its instability, distilled (or any essentially pure water) is never used directly. Tap water or other salts must first be added to it in order to increase its GH and KH.
General Hardness (GH)
General hardness (GH) refers to the dissolved concentration of magnesium and calcium ions. When fish are said to prefer ``soft'' or ``hard'' water, it is GH (not KH) that is being referred to.

Note: GH, KH and pH form the Bermuda's Triangle of water chemistry. Although the three properties are distinct, they all interact with each other to varying degrees, making it difficult to adjust one without impacting the other. That is one reason why beginning aquarists are advised NOT to tamper with these parameters unless absolutely necessary. As an example, ``hard'' water frequently often comes from limestone aquifers. Limestone contains calcium carbonate, which when dissolved in water increases both the GH (from calcium) and KH (from carbonate) components. Increasing the KH component also usually increases pH as well. Conceptually, the KH acts as a ``sponge'' absorbing the acid present in the water, raising the water's pH.

Water hardness follows the following guidelines. The unit dH means ``degree hardness'', while ppm means ``parts per million'', which is roughly equivalent to mg/L in water. 1 unit dH equals 17.8 ppm CaCO3. Most test kits give the hardness in units of CaCO3; this means the hardness is equivalent to that much CaCO3 in water but does not mean it actually came from CaCO3.

General Hardness

0 - 4 dH, 0 - 70 ppm : very soft
4 - 8 dH, 70 - 140 ppm : soft
8 - 12 dH, 140 - 210 ppm : medium hard
12 - 18 dH, 210 - 320 ppm : fairly hard
18 - 30 dH, 320 - 530 ppm : hard
higher : liquid rock (Lake Malawi and Los Angeles, CA)


Cheers
Francis

[VIC2008]

i bought a test kit API brand that measures :
GH =general hardness
KH =carbonate hardness
PH = 6.0 to 9.0
NO2 = nitrite
NO3 =nitrate
these are 5 in 1 test strips
FYI
VIC

[jaykne]

Like you have been told your GH is general hardness and kh is basically the amount of minerals stuff like that in your water. Wild Discus come from waters that are low in GH and KH which in turn gives you soft acidic water and a lower PH. My GH is very low due to water softener, but my KH is still remains high about 450ppm, and my PH is around 8. My discus are very healthy and thrive in these water conditions, but from everything I have heard and been reading when it comes to breeding the eggs will not hatch in these water conditions need to get an RO unit and make water for breeders. Unless you are trying to breed, I would say just make sure your PH is stable, and don't worry about your GH and KH. Hope this helps Larry.

[Dubiadiscus]

Thank you so much for this much needed info very well put and easy to understand, thanks francis and everyone else for your input. My tank is currently doing well my ph is at 7.5 NO2 NO3 are at 0ppm. I know my water is soft but not shure how soft without the test. I have well water and it seems to be pretty good strait from the tap. Im just trying to get the tank set up right for the discus i will be getting here in a few weeks.
Thanks again
john

[jaykne]

Thank you so much for this much needed info very well put and easy to understand, thanks francis and everyone else for your input. My tank is currently doing well my ph is at 7.5 NO2 NO3 are at 0ppm. I know my water is soft but not shure how soft without the test. I have well water and it seems to be pretty good strait from the tap. Im just trying to get the tank set up right for the discus i will be getting here in a few weeks.
Thanks again
john

Oh you are in Michigan, I grew up in MI and my dad had a breeding pair of Wattley discus and we had perfect water conditions to even breed right out of the tap. I am now near Jacksonville FL and complet opposite pretty much liquid rock, as long as your ph is stable and you remove any clohrine before adding water you should have no problems.