dH, KH and GH
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Information in books and on the web which specify the water of the fish's natural habitat generally refer only to the "hardness", but the actual measure relates to the GH. GH, or calcium and magnesium hardness, has impact on breeding in a number of fish, as many eggs, specifically the egg membranes, are quite sensitive to those ions. Calcium and magnesium by its presence or near absence, has impact on the ability of sperm to penetrate the egg, and later on the hatching of the embryo from the egg.
Most fish are quite adaptable to both GH and KH (perhaps KH is better thought of as alkalinity or buffering capacity than as another "hardness") for maintenance. Some species do need attention to the GH for breeding purposes, but even those specialized fish as adults are not adversely affected by higher-than-breeding levels of GH.
HTH
Most fish are quite adaptable to both GH and KH (perhaps KH is better thought of as alkalinity or buffering capacity than as another "hardness") for maintenance. Some species do need attention to the GH for breeding purposes, but even those specialized fish as adults are not adversely affected by higher-than-breeding levels of GH.
HTH
I think the original poster is reffering to degrees of hardness, which is a different number to a GH or KH reading.
On the back of my test kit is lists a bunch of different terms like this and has a multiplier to use to convert between the designations.
So dGH = GH x a (where 'a' is some number I can't remember :duh: )
I don't quite understand where those different measuremets are usued and stuff yet either, it's would be good to have a guide to this stuff somewhere.
On the back of my test kit is lists a bunch of different terms like this and has a multiplier to use to convert between the designations.
So dGH = GH x a (where 'a' is some number I can't remember :duh: )
I don't quite understand where those different measuremets are usued and stuff yet either, it's would be good to have a guide to this stuff somewhere.
I think if you multiply the dGH by a number just slightly over 17 (17.3 or 17.4, I think) you get the GH.
I'd look it up but I'm lazy, my hand is in a cast, and the sucker hurts right now. So you can Google it if you want.
I'd look it up but I'm lazy, my hand is in a cast, and the sucker hurts right now. So you can Google it if you want.
What RTR said for the difference between GH and KH.
The other bit is a unit of measurement issue. Some folks and some test kits measure GH and KH in ppm or parts per million, which is conveniently the same as milligrams per liter (mg/l). Others use degrees (sometimes called German Degrees). One degree of Hardness (dH) is 17.9 ppm (mg/l) and is used for both GH and KH.
The other bit is a unit of measurement issue. Some folks and some test kits measure GH and KH in ppm or parts per million, which is conveniently the same as milligrams per liter (mg/l). Others use degrees (sometimes called German Degrees). One degree of Hardness (dH) is 17.9 ppm (mg/l) and is used for both GH and KH.
If you want to be picky it is 17.86, still rounds off to 17.9 
If you read a German text, they are likely referencing hardness as CaO, where we use CaCO3. In that case the convesion number would be 10 ppm per degree of hardness, but that would be terribly confusing on an English-language board. Nobody would ever understand you.
If you read a German text, they are likely referencing hardness as CaO, where we use CaCO3. In that case the convesion number would be 10 ppm per degree of hardness, but that would be terribly confusing on an English-language board. Nobody would ever understand you.
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Oh, fine, be that way!RTR said:If you want to be picky it is 17.86, still rounds off to 17.9
Okay, 17.86 -- 1786, year Davy Crockett was born or the year John Molson founded his first brewery in Montreal. Being Canadian, I'll probably remember the latter one easier
Roan