Water values in General

[Adam - Sydney]

After this week, I realised I have a very basic understanding of water values. I am usually the type of person who needs to understand things to see value in them, but on the case of water chemistry I went with what i was told. I never had any water problems before so I guess in the year and half ive been into fish (seems so much longer) its never been a point on thought. Now I have run into problems I dont understand why things happen.

My questions are firstly basic
What relationship does kH have to pH? (i know low general equals low by why?)
What relationship does kH have to gH and why the difference?
How does very low pH and kH water remain stable and not suffer from large swings?
For say a fish that typically lives in 7.0, 6.5 or 5.0 pH what kH values am i after?

If anyone has any sites that may help me i would appreciate that.

Thanks in advance.
Adam

ps. I like and dislike the fact that in this hobby you can be an expert and beginner in the same day. There is so much to learn and like life its never good to think you have learnt everything.

 

[Pnyklr]

My parameters:
pH of over 8.4 (I think it is closer to 9, but my kit only goes to 8.4)
Total Hardness (GH) 50 ppm
Total Alkalinity (KH) 300 ppm
(I am not sure of the degrees of the GH and KH, only the parts per million)

The KH is the buffering capacity of the water. The higher the number, the less prone to swings in pH. This is generally a good thing, as your fish won't have to deal with the fluctuations of pH.

My KH is so high, that it is nearly, if not, impossible to alter the pH for more than an hour. I have to mix RO water into my tap in order to see any noticable difference in pH. To get it below 7, I will have to mix tap and RO water, and then filter the mixture through peat.

I am surprised that my GH (hardness) isn't higher. I am not sure if the "hardness" in aquarium-speak is the same as hard and soft water that we refer to when talking about the water in the shower (ie soft water allows the soap to lather better, whereas hard water doesn't really lather at all). In my area, our water is very hard. We have to have water softener units in the house to counter-act that.

*For those who don't know,here is my "woman's way" of explaining it: There is a softening tank that the water runs through, and all of the "bad stuff" is absorbed by a material in the tank. After a while, the material has reached the maximum absorbtion, and must be "cleaned out." The softener tank will then take water fromt he brine tank, and regenerate the material so that it may start absorbing the "bad stuff" once again. This is in no way as pure as RO water.*

I am not sure if the water I use for my water changes has been softened or not; I get it from a utility sink in the basement that may not give the treated water.

I hope that helps....I, too, only have a basic understanding of water chemistry.

 

[fishgeek]

difficult subject to cover because to answer correctly will probably confuse the whole matter, many simplifications and generalisations are used and are not always true so will lead to misunderstanding as you learn more

definitions

pH - basically means the power of hydrogen
it is calculated as the negative logarithmn of the hydrogen ions(maths chemistry already!)

Kh - carboate hardness -is a measure of dissolved carbonate and bicarbonate in water and is measured in a german scale where 1 degree of hardness equates to approx 17 ppm
(international units are never the same for anything it's a bit like miles and kilometers or worse gallons and gallons)

Gh - general or total hardness - is a measure of all dissolved minerals or sometimes just calcium and magnesium



your first question
pH is often generalised as being low in low Kh water , this is not exact though the understanding that the Kh measures products that will shift the pH upward may help you understand
carbonates will when dissolved in water bind with hydrogen molecules and are effective at mopping up free hydrogen ions often released in CO2 , H2O reactions ie respiration of fish and to a lesser plants
this leads to carbonates stopping an increase in hydrogen ions and a decrease in pH

the generalisation comes about because most carbonates(kh) in most domestic waters are calcium(gh) carbonates and these will generally stay alkaline , other carbonates can be acidic or relaes hydrogen on decoposition though these are not so common

i guess some of the above answers question 2 aswell

water it self has a constant set of buffering reactions and is not a stable H2O molecule but rather a flux between hydroxly ions and hydronium ions and anything else that maybe dissolved in water
the stablity comes down to the chemistry of the dissolved prducts and in natre the scale of the water vlume and turnover (volume is bufferig swings in nature)

emm not sure that really helps
andrew
the kribs answers
just type in water chemistry in goole and you will get thousands of hits and probably thousands of variations on an answer

 

[Adam - Sydney]

Thank you both for the replies.

To simplify what you have written, am i right in saying an increase in carbonates (measured as kH) will tend to stabilise pH by stopping reactions which lead to an increasing concentration of Hydrogen (and lowering pH). And am I also right in thinking if you can get a water with an amount of kH down to a lower pH it should keep it at that pH or raise it higher.

The answer to my second question would be that an increase in kH will result in an increase in gH due to an increase in elements within the water.

Does this result in a negative effect on soft water fish?

Adam

 

[Mike Wise]

In my area, our water is very hard. We have to have water softener units in the house to counter-act that.

Pnyklr,

If I had your problem I would use water that has not gone through your water softener. Why? Because it replaces Ca & Mg with Na. Since Ca & Mg have 2 free ions & Na has only 1, your water softener adds 2X the number of ions to the water. These ions contribute to increased conductivity (bad for soft water fish). This may be one of the problems that you have experienced with breeding your cacatuoides.

am i right in saying an increase in carbonates (measured as kH) will tend to stabilise pH by stopping reactions which lead to an increasing concentration of Hydrogen (and lowering pH).

Adam,

For all practical purposes this is true - if you can get your pH stabilized at a reasonable (for the fish being kept) alkalinity.

am I also right in thinking if you can get a water with an amount of kH down to a lower pH it should keep it at that pH or raise it higher.

This is true, too, as long as your system (aquarium) does not produce more acids - but it does. Biological activity produces any number of acids that will drive the pH lower once the alkaline reserve is used up. This is why regular water changes are a necessity - especially in soft water systems.