balancing act... water...

[Magnum Man]

so I've come a long way, on my understanding of "water" in the last while, since restarting starting my aquariums... outwardly it seems pretty simple, until you start getting into maybe some specialty fish & areas... maybe I misread this, but seems I was looking at some fish or the other the other day, that liked medium hard water, of low PH...
so if that was the case, I assume there could be dissolved solids other than calcium, that makes the water "hard", but that the water is exposed to enough leaf litter that lowers the Ph??? ... ( calcium buffers the water, but does it buffer it alkaline or buffer it acid, or does it basically make water try to hold that 7.0 Ph ??? ) anyway I'm beginning to find more unusual fish interesting, & I'm sure at some point, the fish will survive if you get the hardness & Ph close... & today, that's maybe good enough, but if you were trying to breed, which I may have interest in, after I retire... Ph may make the difference in something breeding...

 

[Wills]

It sounds like you are stuck in the same research loop I often end up in! It is baffling when you really dive into the effects of hard water and how different habitats experience them, even some South American locations experience pretty hard water in the dry season. I've seen the same results you mentioned too with high ph but low hardness - I think this is often because of the nitrogen cycle in slow moving swamp like locations.

The Badis and Dario species of South East Asia are interesting in this regard, most of the species in the hobby come from still, swampy locations but there are some from limestone, chalk streams in clear, flowing water that will likely have the hardness expected of the higher ph.

Wills

 

[Naughts]

calcium buffers the water

I thought it was carbonates (KH) that buffer water?

 

[MaloK]

Carbonates are considered Temporary hardness, Calcium and Magnesium, it precipitates out of the water and affects PH considerably.

Chlorides are considered as Permanent hardness, Calcium and Magnesium, it does not precipitate nor affects PH as much.

Water can be constituted of both Calcium and Magnesium, Carbonates and Chlorides in different proportions in addition of all the other minerals that could contribute to the composition. Carbonates are buffering and bio available to certain organism, Chlorides contribute to osmotic balance and some fishes that have special requirements.

Botanicals have nearly no impact on water hardness. They will interact with Carbonates to a certain extent, but only in a temporary and minor manner. So Their effects are more evident and lasting in already soft water.

They are used for the living critters in the tank as food and as low molecular weight acids. that contributes to their well being. Like : Formic, Acetic, Lactic, Oxalic, Malic.

Under aqueous condition these wont react much with Chlorides and lightly with Carbonates.

 

[Naughts]

Carbonates are considered Temporary hardness, Calcium and Magnesium, it precipitates out of the water and affects PH considerably.

Chlorides are considered as Permanent hardness, Calcium and Magnesium, it does not precipitate nor affects PH as much.

Water can be constituted of both Calcium and Magnesium, Carbonates and Chlorides in different proportions in addition of all the other minerals that could contribute to the composition. Carbonates are buffering and bio available to certain organism, Chlorides contribute to osmotic balance and some fishes that have special requirements.

Botanicals have nearly no impact on water hardness. They will interact with Carbonates to a certain extent, but only in a temporary and minor manner. So Their effects are more evident and lasting in already soft water.

They are used for the living critters in the tank as food and as low molecular weight acids. that contributes to their well being. Like : Formic, Acetic, Lactic, Oxalic, Malic.

Under aqueous condition these wont react much with Chlorides and lightly with Carbonates.

You lost me about half way through the first sentence…

 

[Magnum Man]

Btw, I certainly wasn’t posting as an authority, still trying to learn

 

[MaloK]

I'm stuck with you guys. As long as I understand to be confident of what I'm doing is not wrong.

I consider that enough for me.

 

[Magnum Man]

Wondering if these could take a turn from chemistry, to natural conditions, as to what in nature makes some of this conditions, it got touched on above listing stagnant water, with lots of leaf litter….
Assuming natural “soft” water, is just not exposed to any materials that make it alkaline, so the mud / sand must be composed of harder minerals, that doesn’t leach into the water, the way limestone does???
I suppose if rain water water makes up a major portion of the water, like in creeks and streams, it would naturally be softer than lake or stagnant water , that collects the minerals???

 

[Essjay]

Water originates as rain, and it's what it lands on/flows over which affects the hardness.

Rocks such as granite do not dissolve to anything more than a trivial degree. Water flowing over it is soft water. In the UK large parts of Cornwall have granite substrate so the water is mainly soft there.
Rocks made of calcium carbonate - chalk and limestone - dissolve easily resulting in hard water - that's why fish keepers living in south east England have "liquid rock" tap water.
In other areas the ground is covered with decaying plant matter - eg the Amazon basin, and this affects the composition of the water rendering it very soft and acidic.


In general terms, tap water is either soft and acidic or hard and basic (that's the chemical opposite of acidic) But there are regions where the water is soft with a high pH or hard with a low pH. But it's the minerals in the water which affect pH, KH and GH.



Hard water is water with a high level of divalent metal ions. Soft water has few of these ions. The ions are mainly calcium with some magnesium and trace amounts of other divalent metal ions. There may be mono- and trivalent metal ions (eg sodium, aluminium) as well but these are not part of hardness.
Hardness is expressed as though all these divalent metal ions were calcium carbonate or calcium or even calcium oxide. This does not mean that hardness is a measure of only calcium carbonate or only calcium or only calcium oxide, it is a measure of what the number would be if all the metal ions were those substances. My younger son used to work an analyst at a water testing company, and he explained it.

He also explained KH, which water providers/testing companies call alkalinity. It's the amount of a specific acid at a specific concentration needed to drop the pH of a specific volume of water to 4.5. KH measures compounds in the water which react with acid and these are almost all carbonates and bicarbonates. A substance which stabilises pH is called a buffer; so KH is a buffer which stabilises the pH of a fish tank. Where KH is high, it is difficult to change pH; where it is low it is easy to change pH.
And just to complicate matters, KH value is expressed as though it were all calcium carbonate regardless of whether the cation is calcium, magnesium or whatever and regardless of whether the anion is carbonate, bicarbonate or something else.


For example, if water is high in calcium, it is defined as hard. If it also contains a lot of carbonate, KH is high. But if the water contains chloride instead of carbonate, KH is low. With chloride and little carbonate there is nothing to buffer the pH so it is low. Even though the water is defined as hard because there's a lot of calcium.

 

[GaryE]

A lot of it comes from learning a little (in my case very little) geology. As I wandered through molly habitats, there was fine white dust everywhere, and the land was clearly uplifted sea bed with a lot of worn and dry limestone and coral. In the Amazon though, most of the rocks have been far from the sea since ancient times, and there simply aren't any minerals left to leach out of them. Millenia of huge rainfalls and weathering has taken care of that.

If we have 100ppm water, there 's no guarantee we have 100 ppm of the same minerals. I think for average hobbyists like us, with no laboratories or sophisticated equipment, all we can count on is being close. It likely doesn't always work, but it usually does. We're reading complex water with really crude tools.

 

[Magnum Man]

@Essjay "And just to complicate matters, KH value is expressed as though it were all calcium carbonate regardless of whether the cation is calcium, magnesium or whatever and regardless of whether the anion is carbonate, bicarbonate or something else."

so if the KH value were other minerals than just calcium carbonate, does it still act as a buffer & resist Ph change??? or at least to the same level as a high KH value, that was actually predominantly calcium carbonate???

 

[Essjay]

If the 'other minerals' also react with acid, then yes they are part of KH. That's why water companies and testing companies use the term alkalinity rather than KH.

My water quality report includes values for cadmium, copper, manganese, nickel which are all divalent metal ions which are part of GH. Unfortunately it doesn't list things which would react with acids (and it does not even mention carbonate or bicarbonate). If there is something naturally occurring in water supplies which does react with acid, then yes it would be part of KH. Off hand, I can't think of anything other than bi/carbonate which would be in the water supply but that doesn't mean there isn't anything else.

 

[MaloK]

@Essjay "And just to complicate matters, KH value is expressed as though it were all calcium carbonate regardless of whether the cation is calcium, magnesium or whatever and regardless of whether the anion is carbonate, bicarbonate or something else."

so if the KH value were other minerals than just calcium carbonate, does it still act as a buffer & resist Ph change??? or at least to the same level as a high KH value, that was actually predominantly calcium carbonate???

Calcium, magnesium and sodium carbonate and bi-carbonate, all act as buffering agents. Magnesium as a slightly greater buffering capacity but the difference is negligible due to very similar acid dissociation constants. And often the presence of more calcium than magnesium.

 

[Essjay]

The only circumstances I can find where calcium acts as a buffer is inside cells not in water. If you have links to calcium acting as a buffer in water, can you let me have them please, I don't like not knowing things

 

[MaloK]

The only circumstances I can find where calcium acts as a buffer is inside cells not in water. If you have links to calcium acting as a buffer in water, can you let me have them please, I don't like not knowing things

I was talking about the Carbonates and Bi-carbonates of Magnesium and Calcium.