Large difference between GH and KH

[msquared]

I had been using test strips initially to check hardness and alkalinity. I since picked up the API liquid kit. The KH agrees on both tests and is very soft (36-40ppm, or dKH=2). On total hardness, though, the strips say 75ppm (dGH=4.2) while the liquid kit says 125ppm (dGH=7). I know it won't be a surprise to anyone that the kits don't agree, and I know it is assumed that the liquid test is more accurate. So let's assume that's the case.

That means my dGH is 7 while my dKH is only 2. That seems kind of "out of whack" because I thought they should be closer together than that. I am hoping to keep my water on the soft side for my Cardinal Tetras and my Blue Ram, and they seem happy. So is there anything I need to worry about, or is this difference not really out of the ordinary? Thanks for any insight anyone can provide.

 

[KarlTh]

Not at all. Your water is mineralised with sulphates, oxides and chlorides rather than carbonates. Hence the KH is low but GH high. You'd get the same if you did the tests on a solution of epsom salts.

Conversely, you can have water high in sodium bicarbonate which has a high KH and a low GH. The two are usually close together because the most common mineral in water is calcium carbonate, but it isn't always like that.

The GH isn't ideal for the rams, although unless you're trying to breed them I doubt the cardinal tetras will mind much.

 

[AquariArt]

I had a similar discrepancy between my KH and GH. My KH was low but my GH took 15 drops to change color! (well off the chart) I purchased a Tap water purifier to lower the general hardness of my water and to lower my PH as well. After using it for the last five water changes the GH is now down to a readable 10 or 179 ppm - I am lowering the GH slowly over time so as to not cause the fish too much stress, mixing at first 40% percent tap water with 60% filtered water, now I use 25% tap water with 75% filtered water.

 

[jones57742]

I had been using test strips initially to check hardness and alkalinity. I since picked up the API liquid kit. The KH agrees on both tests and is very soft (36-40ppm, or dKH=2). On total hardness, though, the strips say 75ppm (dGH=4.2) while the liquid kit says 125ppm (dGH=7). I know it won't be a surprise to anyone that the kits don't agree, and I know it is assumed that the liquid test is more accurate. So let's assume that's the case.

That means my dGH is 7 while my dKH is only 2. That seems kind of "out of whack" because I thought they should be closer together than that. I am hoping to keep my water on the soft side for my Cardinal Tetras and my Blue Ram, and they seem happy. So is there anything I need to worry about, or is this difference not really out of the ordinary? Thanks for any insight anyone can provide.

ms: several years ago when reading the literature I got into some erroneous information and was only "set right" on this Forum a month or so ago. (talking about feeling like an Aggie!)

Kh is carbonate hardness and can be higher the Gh which is general (German) hardness.

Hence the charts which correlate Ph and Kh to CO2 concentrations.

TR

BTW: the game is Thanksgiving again! 7:00 p.m. at Memorial Stadium. I got my 1st class seats in the outdoor area of the new North End Club (which is, of course, reputed to me be much nicer than the Zone Club [which is very, very nice as I have watched many games at the Zone Club]).

 

[msquared]

Hmm, very interesting. I'm not too worried about these levels, I guess. The Ram and the Cardinals are happy and healthy. My real concern would be if either level started to trend upward very much. I'll keep track of things and see what happens.

PS - Jones57742, that's good info. I know what I'll be watching on T-day this year!