Is hardness GH? KH? Both?

[tolstoy21]

Is hardness GH? KH? Both? 

I ask this because when I read fish keeping articles, they all seem to suggest different things.  Some reference only KH as being soft and make no reference to GH. Others suggest GH. Others mention TDS/PPM. My well water is below 1 KH but has a GH of 9. Is this hard or soft? Both? Doesn’t really matter?

I understand the difference between GH and KH and what they do and are composed of. Just totally confused by the loose and various use of the term ‘hardness’ in reference to those.

According to my well test company I have hard, acidic water. My house has both a water softener and a PH neutralizer for tap water. (The low Ph - 5.0 out of the tap - does a number on my pipes).

But like I said, I get confused by what I read in various articles in relation to fish keeping and hardness.

For instance, when someone references ‘soft water species’ is this in reference it KH alone? Because they all seem to mention Ph in conjunction with that, yet my water has both a low Ph and is moderately hard. Right?

The inter webs is totally confusing me!
 

Edited October 13, 2020 by tolstoy21

[varanidguy]

The company is correct. 9 GH is considered hard water, but 1 KH makes it acidic. They're both hardness but do different things.

Usually when articles/people say that something likes soft water, that means a low KH/more acidic water. Carbonate hardness fluctuations can cause fish to shock as this is a key factor in osmotic regulation. Change the value on the fish rapidly and they lose/take on more water in their bodies. Typically it's easier on a fish to go higher in KH than it is to go lower, at a rapid pace anyway.

 

Sounds like it's great water for growing plants, straight from the tap, providing there's nothing else fouling the water.

[tolstoy21]

8 hours ago, varanidguy said:

Usually when articles/people say that something likes soft water, that means a low KH/more acidic water. Carbonate hardness fluctuations can cause fish to shock as this is a key factor in osmotic regulation. Change the value on the fish rapidly and they lose/take on more water in their bodies. Typically it's easier on a fish to go higher in KH than it is to go lower, at a rapid pace anyway.

Thanks for the reply varanidguy.

So when people refer to fish 'soft water' is this specifically in reference to KH/PH/acidity irrespective of GH? 

Are their instances where GH becomes a factor in terms of long term fish health? Are their GH sensitive species?

I don't really have any specific issues I'm looking to fix. I'm just looking to get some clarity around this topic.

 

[varanidguy]

4 hours ago, tolstoy21 said:

Thanks for the reply varanidguy.

So when people refer to fish 'soft water' is this specifically in reference to KH/PH/acidity irrespective of GH? 

Are their instances where GH becomes a factor in terms of long term fish health? Are their GH sensitive species?

I don't really have any specific issues I'm looking to fix. I'm just looking to get some clarity around this topic.

 

Generally speaking, yes that's what they mean in regards to KH and pH.

 

GH is a factor in some instances, but typically the effect is much more mild to the point where it's generally not worried about so long as the water does have some GH in it.

 

Insofar as GH sensitive species...if there are any, I'd wager it would be wild caught fish from naturally acidic and soft environments. But even that's not always the case. For instance, I keep two-spot catfish in my 75 gallon, they are wild caught, purchased as adults and subadults. Their natural habitat is peat swamps, so naturally they come from very soft and acidic water. They are kept in a pH of 8.2 with a dKH of 5. They're doing very well - active, eating, great coloration, no signs of long-term stress. But, if you look up their care requirements, it's always suggested to keep them in biotope aquariums with dim lighting, and very soft acidic water.

[tolstoy21]

Thanks again varanidguy!

So much on the internet seems to conflate hardness/softness with alkalinity/acidity in a way that was confusing the heck out of me.

When I'm thinking about my water in terms of fish keeping, I kept asking myself -- "Is my water hard or soft?"

I know it's hard given the GH, but then was stumped as to how to figure in the almost non-existent KH in terms of what is mentioned when people say a specific fish species prefers 'soft water', and then what they go on to describe seems to relate more to acidity/Ph.

For me personally, I have a few tanks I add crushed coral or aragonite to, and I also use RO for caradina shrimp. But when pondering my plain, unfiltered well water, what I was reading online in terms of fish keeping seemed clear as mud.

Something like this on the other hand (taken from non-aquarium literature), seemed more accurate to how I was thinking about the topic:

Quote

Alkalinity and water hardness are fairly similar--essentially they both come from sources in nature. Water moves through rocks (and picks up minerals as it does so) on its way to rivers and lakes. When limestone and dolomite dissolve in water, one half of the molecule is calcium or magnesium (the "hardness") and the other half is the carbonate (the "alkalinity"). This means that the level of water hardness and alkalinity in a place will be very similar. However, they are very separate measurements, and have very different importance.

I grabbed this snippet from: https://extension.usu.edu/waterquality/learnaboutsurfacewater/propertiesofwater/alkalinity

[varanidguy]

1 minute ago, tolstoy21 said:

Thanks again varanidguy!

So much on the internet seems to conflate hardness/softness with alkalinity/acidity in a way that was confusing the heck out of me.

When I'm thinking about my water in terms of fish keeping, I kept asking myself -- "Is my water hard or soft?"

I know it's hard given the GH, but then was stumped as to how to figure in the almost non-existent KH in terms of what is mentioned when people say a specific fish species prefers 'soft water', and then what they go on to describe seems to relate more to acidity/Ph.

For me personally, I have a few tanks I add crushed coral or aragonite to, and I also use RO for caradina shrimp. But when pondering my plain, unfiltered well water, what I was reading online in terms of fish keeping seemed clear as mud.

Something like this on the other hand (taken from non-aquarium literature), seemed more accurate to how I was thinking about the topic:

I grabbed this snippet from: https://extension.usu.edu/waterquality/learnaboutsurfacewater/propertiesofwater/alkalinity

That is a much better way than I could explain it. lol

 

Your water without crushed coral should be fine for keeping soft-water fish. So long as there's at least one degree of carbonate hardness, the pH should remain stable (providing that value doesn't change from other sources). With 9 degrees of GH, your water doesn't really need any additional GH. BUT if you're having success with crushed coral, then why change it? Just some food for thought.

[tolstoy21]

I use coral and aragonite for things like shell dwellers, or fish that 'prefer' something above neutral. 

I get a Ph of 7.4 - 7.6 by adding some Top Fin coral into the substrate or bubbling it in a small box filter, and something closer 8 with aragonite. The coral gives me a level of confidence I'm not suddenly going to run out of KH and have a unexpected Ph drop. 

For 'soft-water' fish I'm just using the plain well water (taken from a line that bypasses the water softeners, etc.). This gets me closer to a Ph of 6.8, with a KH around 1.  These were the species I was thinking about when I asked the original question concerning is hardness GH or KH.

I know the advice is to not 'chase the Ph' and just make sure it's stable. But adding some coral to some tanks is easy enough to maintain without hassle.

Again thanks for the answers. Was really just trying to get clarity around the topic. This brief conversation helped!

Edited October 13, 2020 by tolstoy21

[varanidguy]

I think your methods are perfect. I've personally seen African rift lake cichlids kept in low pH water and it's not pretty. They are one of the fish, I think, where it really matters. They should definitely be kept above neutral long term.