Please Help with water chemistry!

[mrdee]

Hello everyone,

I have a 40 gallon long tank with a few fancy plecos that I would like to try to breed. My tap is at 7.6 PH with very hard GH. I bought some RO water from the store and did a 50% water change with it. Then I added some Seacam Discus Buffer and lowered the PH to 6.0. I monitor my aqurium every day sinced I added the buffer. Everyday for a week, my PH is reading at 6.0 (acidic), nitrate is at 20 (safe), nitrite is at 0 (safe), alkalinity is at 120 (ideal), and GH is at 300 (very high). I thought that if your PH is low then your water should be soft as well. Why is my PH low but my water still very hard?

Any help would be appreciated!

Dom

[Birger]

I will hope the chemists of the bunch explain about your water, (as I would probably just mix you up)
But I would suggest telling us which species(or L-number) of pleco it is you are trying to have spawn as that would help in suggesting a good course of action and not all of them need the same water parameters.

Birger

[Bas Pels]

As you noted, pH and hardness have nothing to do with each other.

Hardness relates to the amount of calcium and magnesium. Nothing more, nothing less. This is, incidentally, something which came from laundries, as calcium and magnesium both reduce the soap activity.

pH relates to the amount of H+ (I should say H3O+) and OH-. We all know water is H2O, and obviously H+ and OH- = H2O

This, however goes both ways, every moment some watermolecules fall apart, and the rests will, sooner or later, recombine into water.

However, if someone would add something to the water which is -more or less - able to hold H3O+, the relative amount of OH- increases (after all, the H3O is kept elsewhere) and thus the pH increases - the water becomes alkaline

one can also add OH- (such as sodium hydroxide), or H+ (sulfuric acuid, for instance)

The point will always be, more of H+ means less OH- and the other way around

(for those not afraid of mathamatics, the concentration of H3O in pure water is 0.0000001 mol/liter, that is, the zeventh digit behind the dot is not sero. Taking the logarithmic of this, and remouving the mius sign results in a value of 7. thaking a logarithmid and multiplying by -1 is what the p stands for, and the H means concentration of H
If we increase the concentration of H3O, to 0.00001 mol/liter, that is, the fifth digid bihind the dot is not zero, the pH will be 5. ore acid, and a lower value
if we add OH-, the concentration of H3O will decrease, and therefore values like 0.0000000001 mol/liter - the tenth digit is not zero, thus a pH of 10, can be seen)

Well, back to aquariums. People adding calcium to their tanks most often use chalck - that is calciumcarbonate. The calcium will increase the hardness, the carbonate reacts with H3O in the water, remouves H3O and thus increases the pH

If one would add calciumchloride, the hardness would still increase, but the chloride is inactive in pH matters

If one would add hydrochloric acid, HCl, this will fall almost completely apart in water, into H+ and Cl-. The H+ will decrease the pH, and the Cl-does nothing. Therefore hydrochliric acid is a very strong acid

Adding sodiumcarbonate will increase the pH (carbonate = carbonate, soo above) and the sodium is not something measured in hardness


On a sidenote, fish are not soap, and for fish hardness is less important than osmotic pressure. This osmotic pressure comes from everything which is dissolved in the water, and therefore adding NaCl (common salt) will, for a fish, be quite equal to adding a similar amount of CaCl2 (ignore the 2, this would need another expalnation of this length)

[MatsP]

Whilst I agree with Bas's actual statement of "Hardness and pH are not unrelated", I would like to point out that natural hardness in water is often caused by chalk - calcium carbonate, which is a substance that makes water naturally hard and alkaline. It is difficult to find a place in this world where tap-water is both hard and acidic.

Now, back to aquariums. In my view, pH is not the key here. Hardness is. Fish are much more sensitive to osmotic pressure (mineral content in the water) [1] than they are to actual pH values (given reasonable range in relation to their natural habitat, of course - keeping a Tanganyika fish that naturally lives in water of pH 8.0 in water that is pH 6.0 would probably be a bad idea, even if the mineral content of the water corresponds to Tanganyika hard water).

So having hard water that is "the right pH" is probably the wrong place to go. You should try to get the right hardness (although avoid extremely soft water - at least make sure you have sufficient KH to keep the pH stable), and then the pH will should follow nicely, rather than adding more minerals in the form of a buffering compound.


[1] Osmotic pressure is the desire for water on one side of a barrier to equalize itself with water on another side of a barrier - the water want's to dilute higher concentrations, so if the mineral content is higher outside the fish than inside it, water will try to get out. If the body has more minerals than the water, the water will try to get into the fish. Fishes are designed to resist this to a certain extent, and uses it to keep their balance of minerals in the body. Too much or too little osmotic pressure will cause imbalance in the minerals in the fish's body.

--
Mats

[mrdee]

I would like to thank everyone that replied back to my original tread. Thanks for the very useful information and your time. I am just a newbie, and learning new things everyday in the fish hobby.

After reading all your replies, now I understand that Ph and GH are totally different. I am glad to see that people here cares for others and helps unexperienced people like myself.

Dom

[racoll]

mrdee, have a read of this.

It should answer many of your questions.

Bear in mind when people say "hardness", this can mean different things. All should be explained in the article.

[mrdee]

Thank you so much "Racoll"! Plenty of useful information and everything makes sense now.

Great people on here!

Dom