Difference between PH and Hardness?

[mooseman]

First of all, thanks to everyone for their great advice and thank you for putting up with my "newbie" questions.

This is related to my last thread. What is the difference between PH and Hardness of water? Should I be concerned about hard/soft and most importantly....how do I know what my fish like when it comes to hard or soft water????


1 - Oscar
2 - Bala's
1 - Sevrum
1- Shovel Nose
2 Moray Eels
1 - Golden Pleco

Thanks!

[Serrateeth_2002]

PH is potential hardness,KH is carbonate hardness,i'm confused,what's the difference?PH is acidic,neutral or alkaline,KH is soft,neutral or hard,these things usually coincide with one another like ph 8 usually is hard water,i hope i am right because i am confused as well.:confused:

[Richer]

pH is the measure of hydronium ions in your water (H3O, or H+). Its a measure of the acidity of your water. kh is a measure of the amount of dissolved carbonates are in your water. kh can determine the pH of your water, due to its ability to buffer your water.

In order to determine whether your water is "hard" or not, we're going to need to know your kh levels. Get a test kit to determine this. In most cases, most fish can adapt to living in water harder than what they usually live in.

HTH
-Richer

[Anton Wernher]

pH is used to measure the acidity or alkalinity of the water. 7 is neutral, the number increases as the alkalinity rises and decreases with increasing acidity.

There are two types of hardness talked about in aquaria.. that is kH and gH

kH (carbonate hardness) This is derived mainly from carbonate and bicarbonate ions. The number reflects the buffering capacity of the water.

gH hardness, on the other hand, refers to the concentration of magnesium and calcium ions I believe. When people refer to a fishes preference as far as hard or soft water goes they are refering to gH.

[Serrateeth_2002]

I really must note this down for my chemistry class,how do hydronium ions get into the water and what are they?I must get more details.

[JamisonBWolsh]

you have some nice fish in there. How big is your tank?

Also, if you have high nitrates, that can lower your PH.

[Anton Wernher]

As to the other part of you question I decided to neglect for whatever reason.. You shouldn't be to concerned with hardness. If you kH is overly low you should be concerned with the possibility of a flucuating pH. As far as gH as long as it isn't to extreme in either direction most fish can adapt quite well(within reason). An incorrect gH will affect the transfer of nutrients and waste through cell membranes. This can affect egg fertility and the fuction of the fishes internal organs.

You can find out what water conditions your fish prefer by where they are found naturally.

[wetmanNY]

Two excellent places to start with alkalinity ("KH" or "carbonate hardness"), which is connected to the balance between pH ("exponent of the hydrogen": acid/base scale) and carbon dioxide, and with general hardness, which is the measure of total hardness, including the KH, and isn't so directly connected with pH:

One is Adrian Tappin's website "Home of the Rainbowfish." http://members.optushome.com.au/chelmon/ open the "Contents" section.

The other is-- as always-- www.thekrib.com

Once you've looked through these two resources, you'll have much more focused questions. Come back and ask them here!

HTH!

[O-man21]

I don't really pay attention to what they mean, I just test them to see if there right or not

[wetmanNY]

That's fine if you're living at 123 Fake Street, but not helpful for folks asking about these things here, is it?

[JamisonBWolsh]

at 123 FAKE street, is it ok to keep a 10 inch oscar in a 5 gallon tank? :)

[morleyz]

I believe this is correct...a basic way to look at this is, if you know that pH is a function of the H+ ions in your water (it's the one thing I remember from chem class. pH = the negative logarithm of the molar concentration of hydrogen ions in a solution)

Anwyay, KH (buffering capacity) is a measure of carbonate (CO3). I believe how this ties pH, KH, and CO2 is:

2H+ + CO3-2 -> CO2 + H20

So...basically if you add acid to your system with a high KH, the buffer (co3) reacts with the excess H+ ions to form carbon dioxide and water. Thus you have buffering capacity.

pH tends to be high with a high KH because most of the H+ ions are reacted with, so there is obviously a lower concentration of H+.

I'm jumping to conclusions on this one...but higher KH solution would have a higher CO2 content? Generally speaking of course...

This is out of distant memory...so feel free to correct where necessary.

[Richer]

Erp, my bad... was going a bit too fast for my own good.

pH is actually the negative log of the concentration of hydronium ions in your water.

Hydronium ions are basically the H+ ion acids give off when they dissociate. Water can also do this:

H2O <-> H+ + OH-

So technically, water is also an acid =)

-Richer

[RTR]

For more than you want to know:

http://www.tomgriffin.com/aquasource/hardwater.shtml

[mooseman]

Thanks everyone for the information, I can see that I am going to have to brush up on my chemistry, this hobby just keeps getting more interesting.

JamisonBWolsh - My tank size is 150 Gallons. The fish are still young but they are growing and get better looking each day...at least I think so.

[Harry Tolen]

I agree with WetmanNY as to the best sources for further information. In very general terms, however, pH reflects the acidity/alkalinity of your water, while KH (carbonate hardness) indicates the tendency of your water to return to neutral or higher pH. GH tends to move in the same direction as KH, but because it is reflective of different chemical components, does not "buffer" the water in the same way.

How you feel about these three different measures of water "quality" will, of course, depend on what fish you are trying to keep and what your maintenance habits are.

[wetmanNY]

RTR, please excuse me for leaving out your Aquasource article, "What? the water's hard?" ( your link) which is one of the best introductions to what the chemistry of carbonate buffering means for aquariums.

[Faramir]

One of the confusing factors is that the KH is often referred to as "alkalinity", whereas in fact it doesn't necessarily refer to pH. I often think it would be better if we avoided that usage.

You can have very high pH water with low KH - a solution of sodium hydroxide in distilled water for example. Equally, you could put hydrochloric acid in high KH water and have an acid solution. In nature, it so happens that KH and pH tend to vary together.

[RTR]

Faramir, KH is technically carbonate hardness, and serves as a measure of "alkalinity" (carbonate buffering, not whether or not the tank is acid or alkaline in pH). Confusion arises because the KH tests are titrations to an end point, and can be seriuosly distorted by non-carbonate buffers in the tank (phosphates in particular, but also by peat and tannins and other materials) to give invalid results. Water treatment in this country tends to add short-lived alkalis to hold the pH up while the water is the network/pipes. This too can give a distorted picture as the normal, natural waters relationship does not hold here either. The bottom line is that if the water traeatment or the hobbyist has done anything to alter the "natural" pH and KH of carbonate buffered water, neither pH nor KH is particularly useful in analyzing the water. But for folk who require knowledge of carbonate buffering, it is the only game in town.

Wetman, no biggie, it has been in the hopper a while, but not printed till this month due to server issues. It is "new" for public access.

[Faramir]

I know; what I was drawing attention to is the way something referred to as "alkilinity" does not actually refer to the pH of the water; confused the hell out of me at one time!

[Serrateeth_2002]

Can somebody summarise,i'm getting confused:confused:

[wetmanNY]

Briefly, what do you mean "getting?"