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Having a hard time understanding kh and gh


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Hi all,

As my tank comes towards the end of its cycle (yes I have been checking my water daily, yes people on this forum said I probably shouldn't because it would drive me crazy, no I do not regret it. My ammonia spiked and dipped and my nitrite spiked and is dipping now, so the end is near), I realize there are two things I have not paid enough attention to: KH and GH

I purchased the API water tester for gh and kh and it took 6 drops for the kh to change to whatever the specific color needed to be and it took 12 drops for the gh. I understand that means my water is hard. That is about all I understand though (and I should have known, my bar soap doesn't last hardly at all).

What does it all mean?! And how do I find a reliable source to find out what parameters each type of fish needs? I was browsing the web to try to see if the fish I wanted all had similar water parameters and, my goodness, no two websites for one specie listed the same parameters. It only adds to my confusion about gh/kh honestly.

I guess--since my water is hard, should I try to add water softener? Is adding driftwood best, or peat moss to my filter, it other methods? I am hoping to get gourami & tetra (haven't committed to specific species yet), kuhli loaches, and maybe otos or corys that don't mind warm water to my tank.

20210318_084759.jpg

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Irene made a good video explaining KH and GH. As for what fish need, generally most fish can adapt to whatever your water hardness and Ph is and it's generally not a problem. It typically is only something to be concerned over when you're trying to spawn them (or are trying to keep the few species that really need softer water to thrive or vice versa). Doing a Google search for "(fish species) water parameters" will usually bring up care information. Comparing several website's information to make sure it's all similar is what I do to make sure it's accurate. 

 

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12 minutes ago, mgudyka said:

Hi all,

As my tank comes towards the end of its cycle (yes I have been checking my water daily, yes people on this forum said I probably shouldn't because it would drive me crazy, no I do not regret it. My ammonia spiked and dipped and my nitrite spiked and is dipping now, so the end is near), I realize there are two things I have not paid enough attention to: KH and GH

I purchased the API water tester for gh and kh and it took 6 drops for the kh to change to whatever the specific color needed to be and it took 12 drops for the gh. I understand that means my water is hard. That is about all I understand though (and I should have known, my bar soap doesn't last hardly at all).

What does it all mean?! And how do I find a reliable source to find out what parameters each type of fish needs? I was browsing the web to try to see if the fish I wanted all had similar water parameters and, my goodness, no two websites for one specie listed the same parameters. It only adds to my confusion about gh/kh honestly.

I guess--since my water is hard, should I try to add water softener? Is adding driftwood best, or peat moss to my filter, it other methods? I am hoping to get gourami & tetra (haven't committed to specific species yet), kuhli loaches, and maybe otos or corys that don't mind warm water to my tank.

20210318_084759.jpg

If your going gourami and tetras, you definitely want soft water. People will say that they will adapt, and surly they can. However, a few generations of "adapting" doesn't erase thousands of years of evolution. 

With your numbers, I'd drop GH and KH in half. The easiest way is to cut your tap water with distilled water. Example, 2 gallons of tap and 2 gallons of Distilled. Then test. Add more distilled if it's too high and more tap if too low.

Long term, an RO/DI system become very cost effective. 

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15 minutes ago, Mmiller2001 said:

If your going gourami and tetras, you definitely want soft water. People will say that they will adapt, and surly they can. However, a few generations of "adapting" doesn't erase thousands of years of evolution. 

With your numbers, I'd drop GH and KH in half. The easiest way is to cut your tap water with distilled water. Example, 2 gallons of tap and 2 gallons of Distilled. Then test. Add more distilled if it's too high and more tap if too low.

Long term, an RO/DI system become very cost effective. 

I'll have to pick up some distilled water on my next grocery trip and look into an RO/DI system. Thank you for the advice. 

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25 minutes ago, H.K.Luterman said:

Irene made a good video explaining KH and GH. As for what fish need, generally most fish can adapt to whatever your water hardness and Ph is and it's generally not a problem. It typically is only something to be concerned over when you're trying to spawn them (or are trying to keep the few species that really need softer water to thrive or vice versa). Doing a Google search for "(fish species) water parameters" will usually bring up care information. Comparing several website's information to make sure it's all similar is what I do to make sure it's accurate. 

 

I will have to watch this video when I get home. I was doing a lot of comparing of multiple websites for specific fish water parameters. I guess I will just have to take averages. 

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@mgudyka I have a 29hex with 5 otos, 5 corys, 11 neon tetras and 1 angel. All of them are soft water fish in the wild but my Gh is over 300ppm (the highest my test strips goes) and KH is around 100ppm. All my fish are doing well and I have had the corys spawn several times (2 batches of eggs were removed and the fry raised then sold and I had a few fry survive in the original tank too). Stability is far more important than chasing parameters.

That said taking a fish out of very soft water and dropping them into very hard water or vise versa can cause osmotic shock. That is why drip acclimation is particularly important when bringing in fish that are used to different water parameters than your tank. 

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8 hours ago, ChefConfit said:

@mgudyka I have a 29hex with 5 otos, 5 corys, 11 neon tetras and 1 angel. All of them are soft water fish in the wild but my Gh is over 300ppm (the highest my test strips goes) and KH is around 100ppm. All my fish are doing well and I have had the corys spawn several times (2 batches of eggs were removed and the fry raised then sold and I had a few fry survive in the original tank too). Stability is far more important than chasing parameters.

That said taking a fish out of very soft water and dropping them into very hard water or vise versa can cause osmotic shock. That is why drip acclimation is particularly important when bringing in fish that are used to different water parameters than your tank. 

Okay thank you for the advice. I will have to buy one of those lines for drip acclimation and make sure my bucket is clean. Thank you 

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Airline tubing works, or what I usually do is put the fish in a container with the water from the bag and leave it next to my tank. Every half hour to an hour I take the small metal condiment cup (it's a 1 oz stainless steel cup) that I use to thaw frozen food for my fish and fill it with tank water to dump in with the fish I'm acclimating. If I start in the morning then by night they are ready to go in the tank. 

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GH and KH both refer to aspects of water hardness.

To me, for aquariums, the important, high-level take aways are these:

  • When aquarists mention 'soft' water, they are mostly referring only to KH and its effects on influencing a water's PH up or down.
  • GH is important to have for healthy plants, as it contributes minerals they require for growth.
  • You can have both low KH and high GH, or vice versa. Knowing what range of each a specific species of fish can tolerate is a good staring point, as well as knowing some fish species are more adaptable than others.
  • GH and KH can be lowered (simultaneously) but diluting the water with RO or distilled water (water that has been stripped of all mineral content).
  • GH and KH can be raised by adding mineralizers or buffers. Here you can adjust either to your liking. 

In the end, taking steps to adjust water hardness creates work and sometimes expense and isn't always 100% necessary for the average fish keeper keeping common, adaptable fish.

I don't think KH 6 and GH 12 are super crazy high readings, all of my fish live in GH 8 and do fine (except the dead ones😉 ).  

Id maybe want to know what my PH was as a result of having a KH of 6. PH is the more important reading. And if that's not super high or super low, i think you should be fine.

Edited by tolstoy21
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12 minutes ago, tolstoy21 said:

GH and KH both refer to aspects of water hardness.

To me, for aquariums, the important, high-level take aways are these:

  • When aquarists mention 'soft' water, they are mostly referring only to KH and its effects on influencing a water's PH up or down.
  • GH is important to have for healthy plants, as it contributes minerals they require for growth.
  • You can have both low KH and high GH, or vice versa. Knowing what range of each a specific species of fish can tolerate is a good staring point, as well as knowing some fish species are more adaptable than others.
  • GH and KH can be lowered (simultaneously) but diluting the water with RO or distilled water (water that has been stripped of all mineral content).
  • GH and KH can be raised by adding mineralizers or buffers. Here you can adjust either to your liking. 

In the end, taking steps to adjust water hardness creates work and sometimes expense and isn't always 100% necessary for the average fish keeper keeping common, adaptable fish.

I don't think KH 6 and GH 12 are super crazy high readings, all of my fish live in GH 8 and do fine (except the dead ones😉 ).  

Id maybe want to know what my PH was as a result of having a KH of 6. PH is the more important reading. And if that's not super high or super low, i think you should be fine.

When I think of water as being soft or hard, I'm always referring to GH. Maybe a typo?

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56 minutes ago, Mmiller2001 said:

When I think of water as being soft or hard, I'm always referring to GH. Maybe a typo?

Yeah honestly Ive seen it refer to either GH or KH (or both), depending on what I'm reading, or the context in which it's being used. Both KH and GH have 'hardness' in their name, but their individual influence on water is different.

For aquarium use, I usually consider hardness to be in terms of KH only because what I read online in relation to 'soft water species' of fish is normally used in reference to PH levels, which is determined by the amount of buffer provided by KH. On he other hand, if someone asked me if my household has hard or soft water, I'd probably say hard. But here I'm assuming I'm being asked about the mineral content / GH.

As an example, my well water naturally has KH 0 and GH 8.  So is that hard or soft? Both? Neither? I have a water softener to reduce my household drinking water GH to 0. But I also have another filter that boosts the drinking water PH into 8s by boosting its KH. Which of these two waters  (my well water or my tap water) would a tetra prefer? Which is hard, which is soft? 

Personally, my feeling is that for the beginner trying to understand hardness in relation to achieving something specific with their tank, the phrase just doesn't convey enough information to be 100% useful and accurate.  It's like trying to unravel the meaningful use of TDS as a measure without understanding what the TDS measurement represents other than 'dissolved solids'.

 

Edited by tolstoy21
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"And how do I find a reliable source to find out what parameters each type of fish needs?"

Indeed!

Several sources, including forum dwellers, may actually merely repeat what they once learned, so "everybody" may be wrong for all we know. Then there's the complication of "works for me!". This of course may or may not mean it'll work for you, because of everything.

Real data from natural habitats may be interesting, but not the end of discussion by a long shot. Guppies' natural habitat nowadays is fish tanks, isn't it...

I think you won't get around making your own assessments, guided by what your growing knowledge tells you are good sources of information.

(Cory made a good point in a video: Any one or two sources of stress may be tolerable, given that all other circumstances are very good. This complicates assessment but it also offers a little leeway.)

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44 minutes ago, tolstoy21 said:

Yeah honestly Ive seen it refer to either GH or KH (or both), depending on what I'm reading, or the context in which it's being used. Both KH and GH have 'hardness' in their name, but their individual influence on water is different.

For aquarium use, I usually consider hardness to be in terms of KH only because what I read online in relation to 'soft water species' of fish is normally used in reference to PH levels, which is determined by the amount of buffer provided by KH. On he other hand, if someone asked me if my household has hard or soft water, I'd probably say hard. But here I'm assuming I'm being asked about the mineral content / GH.

As an example, my well water naturally has KH 0 and GH 8.  So is that hard or soft? Both? Neither? I have a water softener to reduce my household drinking water GH to 0. But I also have another filter that boosts the drinking water PH into 8s by boosting its KH. Which of these two waters  (my well water or my tap water) would a tetra prefer? Which is hard, which is soft? 

Personally, my feeling is that for the beginner trying to understand hardness in relation to achieving something specific with their tank, the phrase just doesn't convey enough information to be 100% useful and accurate.  It's like trying to unravel the meaningful use of TDS as a measure without understanding what the TDS measurement represents other than 'dissolved solids'.

 

I think for the sake of beginners, we should follow science here. General Hardness (GH) is the measure of Calcium and Magnesium and other salts in water which determine hardness.

Carbonate Hardness (KH) is the measure of carbonates and bicarbonates, the buffering capacity of water. Referred to as Alkalinity. 

KH 0, GH 8=Hard Water

Edited by Mmiller2001
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1 hour ago, Mmiller2001 said:

I think for the sake of beginners, we should follow science here. General Hardness (GH) is the measure of Calcium and Magnesium and other salts in water which determine hardness.

Carbonate Hardness (KH) is the measure of carbonates and bicarbonates, the buffering capacity of water. Referred to as Alkalinity. 

KH 0, GH 8=Hard Water

I don't 100% disagree with that statement. But I do find that more people, when thinking about fish, either conflate the two, or are thinking of KH when they are thinking of 'soft water' fish.  Which is why i said I believe 'most' people (at least what i see online) mean KH (correctly or incorrectly), because 'soft' is almost always brought up in the context of Ph, except maybe when talking about plants. Again, why it's confusing to most people and context dependent in the general conversations we see online.

For instance, and this is just a snippet of something one can easily grab online; examples abound --

'Carbonate hardness neutralises acidity, water with a high carbonate hardness tends to have a pH around 7.5 to 8.5 and that pH will be stable.  Such conditions are a precondition for those fish from hard water environments, such as Rift Valley cichlids and Central American livebearers, but can cause problems for those fish that do better in slightly acidic water conditions like South American tetras'

The above mentions Carbonate hardness, acidity, PH and hard water in the course of two sentences.

So what does a beginner do with that information other than be stumped. 'Hardness' in this snippet is context dependent; it seems to imply carbonate hardness. I think? Maybe? The Rift Valley also presumably has a high GH, right? Now I'm confused!

I think its easier for a beginner to grasp the following -- The KH number affects my PH. The GH numbers represents the quantities of some important minerals dissolved in my water. Fish and plants prefer the values of both to be in a specific ranges, but these numbers are independent of one another. Fish that we don't consider 'sensitive' or 'hard to keep' or 'expert-level' usually adapt to a much broader range of GH and KH values. 

I don't mean to suggest you implied differently, but just to give an explanation on why I tend to usually think of water hardness as KH when I think of fish keeping. My experience tells me that when keeping 'soft water' fish, acidity is a more important factor than calcium and magnesium levels, in general, except where extremes of GH are concerned. 

I get it that for beginners, it can be confusing, especially when you read stuff like the above that appears to blend the terminology in way that does not add the clarity needed by most people who are new to aquariums.

 

Edited by tolstoy21
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