Help regulating pH, KH, & GH

[LabTest57]

[QUOTE=TechSupport AN;7183]

When I think of mineral salts I think of magnesium, calcium, potassium, etc. Carbonate salts are carbonate and bicarbonate. Carbonate minerals are calcium carbonate, magnesium carbonate, etc.[/QUOTE]

Gh is usually comprised more of calcium ions and calcium carbonate salts.

[Tech Support AN]

According to an Environmental Toxicology textbook (Wright and Welbourn 2002) the principal components of water hardness are the divalent ions calcium and magnesium. The EPA defines hardness in terms of calcium carbonate equivalents: 1 dGH is defined as 10 milligrams (mg) of calcium oxide (CaO) per litre of water, which is equivalent to 0.17832 mmol per litre of elemental calcium and/or magnesium ions.
In water testing, paper strips often measure hardness in parts per million (ppm), where one part per million is defined as one milligram of calcium carbonate (CaCO3) per litre of water. Consequently, 1 dGH = 17.848 ppm.

I do not recall saying that calcium carbonate dissolves quickly, but that it would begin to dissolve at a pH below 6 and at that point impact your GH by putting minerals back into the water. I do not doubt that over time with a pH of less than 6, you will see calcium carbonate dissolve. However, if you want to do the experiment, we will be very interested to see your pictures. :-)

[LabTest57]

Sorry, I'm not going to be able to show pics. I don't care if I'm wrong, however, I would like to point out that the reason being is the following: I could not get more than 10% of any calcium carbonate to dissolve under a pH of 6---in a 35 gallon tank (I was using) with a calcium carbonate solid that is 2 milimeters thick formed (spread-out) on a 2.5 foot by 1 foot surface. I think that because of the amount of calcium carbonate in the water, any acids that were introduced were neutralized when some calcium carbonate dissolved - increasing the kH (the factor in the acid neutralization).

So yes, overtime it can dissolve completely. It takes strong acids to dissolve a lot of it in a short amount of time.
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Lets get away from this....

New topic (relevant to this thread):


I was doing some calculations on % water changes to time-of-water-change (day/week/month) ratio or whatever.


Okay if my tank starts out with 20 ppm of nitrates and every month it gains 20 ppm nitrates, a 50% water change every month should result in 20 ppm or the intial amount of nitrates (unless the bio-load changes).

If I do a 25% water change every week instead, I would end up with a lot less nitrates by the end of the month through this equation: 20+ (20/~4) x 0.75 = ~ 18 ppm at first week; however, if used as a function you will notice a ~ -0.9 drop in total nitrates compared from the last 25% water change.


So, a higher frequency of water changes with 40%> (less than) water replacement is recommended to avoid pH/gH shock and serves as a better way to lower nitrates and organics, instead of doing large water changes every month(s), right?

I've changed my water change shedules due to this... =)

[LabTest57]

[QUOTE=LabTest57;7189] this equation: 20+ (20/~4) x 0.75 = ~ 18 [/QUOTE]


Avoid "Order of Operations", just calculate from left to right no matter what (I put them in wrong order). :)

[Tech Support LK]

So, in a normal aquarium setting, GH and KH operate independently of one another and the test kits that hobbyists use to measure GH detect divalent cations. One should not get confused that these (GH and KH) are, in fact, separate measurements.

Labtest57, please be assured that this is not abut proving anyone wrong, but instead about making sure the hobbyist is not confused in regard to this aspect.

Your calculations are accurate (assuming your nitrates accumulate at a steady daily rate). Performing more frequent, smaller water changes will be more effective at controlling nitrate levels. Smaller water changes will also most definitely be less stressful on the animals.