pH and Water Hardness

Rather than hijacking Ian's thread on breeding I am posting this here to see if anyone can explain the below in laymans terms!!

I have a question - what is the best way to raise or lower the pH of your water? I often see people suggesting raising it or lowering it but am never sure how. I know there are supliments by Tetra etc to change this but are these any good? Or would you use bicarb etc

Is there any correlation between water hardness and pH? I have been mixing them up me thinks, so confused now! Is there a way to make your water harder or softer? Thanks!

I'll try not to use the true definitions here.

pH and Hardness are 2 different things.

I'll concentrate on hardness in this first post.

The chemical compounds that cause water hardness CAN change pH....but that is not a rule.
Similarly, pH can affect hardness.....but, again, that is not a rule.

You can have very acid very hard water;
you can have very basic (pH>>7 = alkaline) very soft water;
you can have acid soft water;
and hard basic (alkaline) water. And varying degrees between all of them.

Often, however, you will find that natural waters tend to be either:
a) pretty neutral with a lowish hardness; or
b) soft and acidic; or
c) hard and alkaline
(all to varying degrees)

So, in answer to your last question, you may happen to find some correlation....but it is not a rule.

Now, when you start to mess with adjusting pH and hardness then you can start to run into problems such as having very alkaline (high pH) soft water.

Alkalinity.....this is another factor:
this is a measure of buffering capacity; in aquatic water is very often due to carbonate hardness (but it could be other things); it is a measure of the waters ability to neutralise an acid.

So....certain hardness types (carbonate hardness KH) will directly affect and contribute to the pH.

But, general hardness (GH) will only affect or contribute to pH if the chemicals causing general hardness happen to have an affect on pH.....but not all compounds creating a general hardness affect pH.

Now, in Marine water the situation is slightly more complex because of the very high concentration of magnesium and calcium. (I can explain what happens there, but it is not simple and even Masters students in chemistry get that wrong !!).

Calcium bicarbonate will contribute to General Hardness and to Carbonate Hardness....it will also affect pH and alkalinity (it is a buffer).

Magnesium sulphate will contribute to General Hardness, but does not contribute to Carbonate Hardness....it will not really affect pH on its own unless it is very high concentrations (as you might find in the sea).


Raising hardness is quite easy.....simply add some coral gravel or magnesium sulphate (Epsom salts) or some other choice compounds.

Lowering Hardness in a tank is a little bit more tricky. Now it is easy if you don't keep fish in the water.
There are easy methods of softening water that are dangerous to fish.

Moreover, very soft water can be quite unstable.

Peat and sphagnum moss can act to lower hardness somewhat.

You could instal a total de-ioniser......but that should be carefully monitored and you'd need to make sure than only a small fraction of the water is cycled through a de-ioniser.

You could mix water with de-ionised OR distilled (expensive) or RO water when doing water changes.

Do not use any form of domestic water softener....many are only intended for washing machines.
Do not use calgon or similar to soften the water.
Do not use any form of bath salt (sodium carbonate) to soften water even though it does....but it raises the pH to potentially very high levels.

As said, if water lacks hardness (especially carbonate hardness) then not only is the pH buffering capacity reduced but there is an added double whammy of a acid crash from the biological filtration system.
You're also in the realms of unstable RedOx (but that is another story).

I'll leave that there for now, and see if you there any questions.

ian

OK, blatant Threadjack here ! I am stumped on this.... how the Hell does Salt in domestic Water softeners, soften Water ? Ian, if you reply, please pretend I'm six years old!!!

Kev.

stretnik wrote:

OK, blatant Threadjack here ! I am stumped on this.... how the Hell does Salt in domestic Water softeners, soften Water ? Ian, if you reply, please pretend I'm six years old!!!

Kev.

Most of the domestic water softeners are of the Permutit type that exchange the calcium and magnesium for sodium (well....it is the ions it exchanges).

The permutit style water softeners (or ion exchangers) are made of a sodium aluminium silicate (a clay).

When hard water with calcium or magnesium is passed over it, it will take in the Ca and Mg ions and give out sodium ions.

To replenish the resin, sodium chloride salt is added...in a saturated concentration.....that will 'drive out' the calcium and magnesium and replace them with sodium: hence, it is recharged with sodium and ready to soften again.

The sodium chloride salt itself does not make the water hard nor soft.
In a dishwasher, however, having salt added will often help the detergent.

Another salt, Sodium Carbonate, will directly soften water....that is basis of the washing machine softening tablets and bath salts. But it will also raise the pH very high.

Ian

Jeez Man, wouldn't the World be a very boring, uninteresting place without Education, thanks for taking the time to explain.

Kev.

Thanks Ian. I'll sit down and give it a proper read tomorrow to try to understand. Too tired at the moment for the brain to work!

PompeyBill wrote:

Thanks Ian. I'll sit down and give it a proper read tomorrow to try to understand. Too tired at the moment for the brain to work!

You asked a lot of questions....so you weren't gonna get a 3 liner reply.

@Kev...no probs. I guess that I owe many many years of learning to the tax-payer....we were always told at college that we, as science students, have a major responsibility to the tax-payer. I'm happy with that philosophy on life.

ian

Hi Ian,
these days, it's probably l'Oreal who the grattitude goes to.
It's funny how I am blaming the "erricatous(sp?)-safe" pea-gravel in the 80l (20l bog-wood, peat etc) for the fact that, despite 1.5 yrs of wc's with RO, lots of blackwater extract, I still get readings of 6.0 pH, 100 micro-seimens conductivity. I think the white pebbles might be to blame.
However, I'm afraid to do a sudden substrate change to black gravel (glass) either.
Mabye 1 kilo per week of substrate would work?
T

murph wrote:

Hi Ian,
these days, it's probably l'Oreal who the grattitude goes to.
It's funny how I am blaming the "erricatous(sp?)-safe" pea-gravel in the 80l (20l bog-wood, peat etc) for the fact that, despite 1.5 yrs of wc's with RO, lots of blackwater extract, I still get readings of 6.0 pH, 100 micro-seimens conductivity. I think the white pebbles might be to blame.
However, I'm afraid to do a sudden substrate change to black gravel (glass) either.
Mabye 1 kilo per week of substrate would work?
T

@Murph.....I must admit that Glaxo and the Welcome Pharmaceutical Trust did pay for some of my years of study.
But, you're right when it comes to the trends. I'd have been quite happy to have been on a L'Oreal scholarship ....maybe I'm worth it.

What fish are keeping?
the pH and conductivity is pretty good for cardinals/discus and would even be close to the breeding conditions for chocolate gouramis.
Although the bog wood and peat would possibly only be pushing out weak electrolytes to continue to keep the conductivity at 100 uS/cm, and fish waste will soon add some pretty good electrolytes (nitrates are nicely soluble), the gravel may not be a inert as expected.

On the otherhand, if it is not totally inert then it may be adding to the stability of the water.

Maybe it is ericaceous friendly because it has a nice supply of iron (as it is generally the locking of the correct form of iron in calcium soils that is a problem for heathers and azaleas etc).

ian

Hi Ian,
Everyone's worth it! (x-factor excluded. See other...)
This tank has 2 farlowella (girls! Boy needed. Story of my life, before Gav says it!),
about 10 glowlights, currently 4 embers left out of 6 (2 years plus old, so the rest going soon),
a male pandourini,
3 male and 2 female dicrossus fillamentosa (lay regularly!)
and 7 ottos.
Also, 1 dwarf puffer! (Snail control. He needs to go to the 180l soon. Once i figure out the shock management routine, or how to catch him. Whichever comes first).

I was trying for more blackwater conditions to try and get the dicrossus fry to survive. (I know, swap the eggs with ones from a useful mother!)

Mabye time to go back to 50%wc/week. Works for the ottos at the equinoxes! Still, the marble pebbles might be problematical. + the farleys HATE any change.
Decisions, decisions.