View Full Version : GH and KH - Should I care?
aquanewb
02-02-2005, 12:40 PM
What are these things? My Master test kit doesnt test for it. Should I care about it? If you need any info about the tank just ask.. I am watching the thread.
Karnaaj
02-02-2005, 12:55 PM
GH and KH are two measures of hardness in your water. In an unplanted tank the two times it becomes really important is if you keep African Cichlids or want to breed fish. In the case of Africans you want to keep the values high. In the other case some fish are only able to spawn successfully if the hardness is kept in a certain range.
In a planted tank (like yours) the values are important to help determine the kinds of plants you can keep. Most plants do not do well in hard water. In addition if you ever want to supplement with CO2 you'll need to know the values because it can affect your PH.
Harlock
02-02-2005, 12:56 PM
Well, seeing as how you have a planted tank, yes, you should care. KH will help you determine how much CO2 is in your tank. I believe (though I may be remembering incorrectly) that gH helps in figuring out things like buffering capacity. Someone correct me if I am wrong, please.
moonbaby
02-02-2005, 3:28 PM
I was wondering the same thing. Where can you get test kits for it, or can you?
Kasakato
02-02-2005, 3:37 PM
Your LFS should have them. I recomend AP's GH and KH test kit.
It is not true that aquatic plants do not do well in hard water. Bad info.
Slappy*McFish
02-02-2005, 6:16 PM
Read through this thread...
http://www.aquariacentral.com/forums/showthread.php?t=35281
KH/carbonate hardness/alkalinity and buffering capacity - determines stability of pH.
GH/general hardness/total sum of all dissolved solids/but test kits generally deal with just calcium and magnesium concentrations.
Most plants do very well in water of 3-5dKH and 6-12dGH.
Die Putzfrau
02-03-2005, 10:03 PM
GH and KH are important in the sense that they both relate to PH. For example hard water (high GH) tends to have a high PH as well as a high KH. Because of the high KH in hard water it makes it more difficult to lower the PH. I would say it's good to know all three of these especially about your tap water.
GH does not influence pH. GH is not total dissolved solids (TDS) at all, it is calcium and magnesium ions.
KH does control pH in unadulterated water.
Slappy*McFish
02-04-2005, 12:52 AM
Here is another article I found that explains 'hardness' fairly well.
http://www.aquariumpharm.com/articles/gh-kh.asp
..and
GH is not total dissolved solids (TDS)
I stand corrected. :)
Die Putzfrau
02-04-2005, 5:11 PM
Yes this is true, GH is not TDS, but GH influences KH which in turn influences PH. GH is derived mainly from the amount of cations Mg and Ca in water. KH is derived mainly from the amount of anions HCO3 and CO3 in the water. These cations and anions can form ionic bonds changing the buffering capacity of the water which affects the PH. So I guess GH doesn't directly affect the PH, but it still does in a way. This one website I looked at said that hard water always tends to have a higher PH.
Kasakato
02-04-2005, 5:47 PM
Is there any way that you can test for TDS?
Die Putzfrau
02-04-2005, 5:57 PM
Well technically no you can't since there are some very very small amounts of ions dissolved in water that really don't make a difference whether they're there or not. For example there might be 10 atoms of copper dissolved in a body of water. This exteremely small amount would have no effect on anything. It couldn't be picked up by any ordinary test that's available in stores. There's really no need to find the TDS in the first place.
Watcher74
02-04-2005, 10:22 PM
GH is what determines the traditional meaning of hard water.
A water with high GH is "hard" to produce lather with soap.
KH is the amount of carbonates/bicarbonates in the water. According to my water report these are extremly high in our local source.
GH tests for Calcium and Magnesium. According to my water report these are extremely low in our local source.
Since these two tests, test for different things, how can they affect one another?
There are filtration methods that will drop your GH to nil and hardly affect KH one iota, which makes me doubt the assumption that these two types of hardness influence one another.
But if this is wrong, and someone can enlighten me, I will be very grateful and interested to know how I am misunderstanding.
Watcher - you are correct. GH is calcium and magnesium hardness, which has no effect on KH or pH. GH reflects whether or not it is "hard" to make a lather with soap. GH also affects the egg membranes of certain blackwater fish, making them hard to breed in higher GH water. Many water utilities treat the water to knock down Ca and Mg, to reduce scale build-up in pipes.
In most natural waters the GH and KH reflect the rock over and through with the surface or subterrainian water has traveled - if limestone is involved at all, both will be elevated and the pH likely will be high, but that does nor mean that GH affects the pH, only that the source of the GH also provided KH (carbonate and bicarbonate) in parallel with the Ca and Mg. There is a lot of limestone in the world, and carbonate/bicarbonate is the buffer system found in most natural waters. Only in places of torrential rains and their washing out of all soluble materials over geologic time do we see blackwater - as in the rainforests of the tropics, the costal rainforest of the Pacific Nortwest, and some restricted areas in the Applachian highlands
Die Putzfrau
02-04-2005, 11:28 PM
Good question, after thinking for a while I realize that there's something that I must know first. Now does GH and KH measure the amount of Mg, Ca, CO3, and HCO3 all together? Or is it only the amount of these substances that remain by themselves, not bonded to anything else?
Regardless of what the answer is, I'm still sure that the amount of Mg and Ca does affect the buffering capacity.
aquanewb
02-05-2005, 12:15 AM
Oh my goodness! It certainly seems like its a miricale that I was able to keep fish and plants alive for any amount of time when I was a kid. I have ordered GH and KH kits since I would like to have a plethera of plants at some point. Thanks for the info everyone. I see that there is a whole lot to know about a whole lot of stuff!
GH is a measure of the Ca++ and Mg++ ions in the water. Ions are just that, themselves, not associated with other things. KH is a measure of the alkalinity of the water, the ability of the water to resist pH change, and in unadulterated water is generally a good approximation of the HCO3- (bicrbonate ion) and the CO3-- (carbonate ion) in the water. If the water is adulterated by addition of commercial buffers, pH adjusters, etc by the hobbyist, or phosphates or orthophosphates at detectable levels by the water utility - then the KH measure will be less accurate to useless.
Die Putzfrau
02-05-2005, 5:04 PM
Oh I see, thanks. But don't the Ca and Mg cations form ionic bonds with the HCO3 and CO3 anions in the water? If this happens, I don't know why it wouldn't, then that means that the GH influences the KH. Can someone clarify this for me?
These materials are fully ionized. If you dry the water out, as the concentration of the minerals in the water get higher from loss of water volume, they will fall out as carbonates and bicarbonates, among other salts.
pjfish
02-11-2005, 12:09 AM
Do I understand correctly that gh and kh are only important if you have plants or want to breed fish? I have all plastic plants and don't plan to have little fish babies. When I did the 5-in-1 test strip, I saw that the KH is 180 and hardness is 300. In case it matters, pH is about 7.8. Nitrite and ammonina are 0; nitrate is < 20. Should I be concerned about gh and kh?
GH and KH and always important. They are the the "hardness" and "alkalinity" of the water. They can each build up in the tank water depending on substrate and rockwork used, or alternately may be depleted in a tank. You always need to have some idea of what your water parameters are, and whether or not they are stable. If they are not stable, you need to figure out why they are not and take corrective action.
But most hobby fish in community tanks on most public water supplies in the USA will be fine without modifications. Unfortunately "most" never means all, so if you don't know what the parameters of your water are, you could be at risk.
pjfish
02-18-2005, 12:25 AM
RTR - I just checked out your tank specs. WOW!!! How big is your tank room? How long have you been doing this?
The tank room is small, 8x14', but the long wall between it and the pool room is fake, so all the tanks on that wall are visible from the adjacent room and serve as display, such as it is (these are hardy "show" tanks).
I've been playing these games since teen-age/pre-teen, so over 50 years. There were times in college and grad school that tanks were semi-temporary. And there have been periods with >40 tanks.
Die Putzfrau
02-18-2005, 4:55 PM
These materials are fully ionized. If you dry the water out, as the concentration of the minerals in the water get higher from loss of water volume, they will fall out as carbonates and bicarbonates, among other salts.
RTR,
Were you answering my question that I posted a while ago with this post? If you were, I still don't understand how this would answer my question, so could you explain it more thoroughly for me please?