Hi all,
I did delve into the chemistry somewhat but its not an easy subject I find.
I know, it isn't easy. I'm not a proper chemist (I'm a botanist) and I've really struggled with the application of some of the concepts.
I'm lucky that I've worked with people who can explain "buffering" etc to me in terms that I can understand. I've also used "@gerald", "
@Mike wise" and <"
@regani"> on Apistogramma forums and they have been very useful, because they are really experienced fish keepers and scientists.
Your results are probably about what you'd expect, you've removed some of the ions and the conductivity has fallen (the TDS measurement is really an electrical conductivity measurement). We know that the dGH should still be the same (we haven't removed any of the permanent hardness) so that is probably to do with the way the test kit works. I'll add in
@alto, he is a lot more up on these things than I am.
You could measure the dGH accurately (by combining the values for magnesium and calcium ions) with an
<"ICP or AAS analyser">, the actual procedure is pretty straightforward, but you need access to the equipment.
The change in pH is a bit strange, you would expect the pH to be much the same (you still have some carbonate) and about pH8. The pH is to do with the CO2 ~ carbonate equilibrium, basically if you have bicarbonate in solution you will always end with a pH about pH7.8 - pH8. The amount of acids you have to add to lower the pH depends upon the reserve of bases ("buffering"), if you have soft water (this is "dKH" we are interested in) a small addition, of weak acids, will reduce pH. If you have hard water then you need to add a lot more acid before the pH falls.
In practical terms it is really difficult to remove solutes from water, without an RO unit, and your water is quite hard, so even the reduction in temporary hardness still leaves you with fairly hard water.
I'm a rain-water user, I know it isn't for every-one, but I've never had any problems with it.
cheers Darrel