Salifert Test Kit Question (KH/ALK)

[Sumpin'fishy]

I recently bough the Carbonate Hardness/Alkalinity Test kit from Salifert. I have a few of their other kits and really like them. This test, however, is a bit difficult for me to understand. Anyone else use this kit now or previously?

First of all what does how can hardness determine alkalinity? From all my research alkalinity is the reverse of acidic; in other words, any pH reading above 7.0. My understanding of Carbonate Hardness is the bufferability of the water (basically, how difficult it is to change pH). Am I grossly mis-understanding?

Secondly, could someone explain what the chart that comes with the test means? I just don't know if my water is hard, medium, or soft. After testing my water I came up with .66ml's. On the chart it has two columns after this:
--my KH value in dKH is: 5.4 (is this hard/soft, what's avg?)
--my Alkalinity in meq/L is: 1.94 (what does this mean?)

Thanks alot for any help.

 

[RTR]

Hardness is an awful term. In fact, alkalinity is not much better. If you wish make up your own term and call it "blifix" or "smerdlu" or whatever, just translate before you post on the boards, please. Hardness should be reserved for calcium and magnesium ions, and referencing whether fish are from hard or soft water - meaning calcium and magnesium rich or poor water.

KH, carbonate hardness, alkalinity, alkaline reserve, or whatever you choose to call it is a measure of the carbonate/bicarbonate present in the water. That is also (if you have not added any other buffer or pH adjuter) a measure of the buffering capacity of the water. If you want the whole deal, try:

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

If you want the significance only, your water is fairly to moderately soft (for KH) but has sufficient natural buffer to be pretty stable. You could use CO2 added to planted tanks without danger. You should monitor the tank(s) periodically (same for nitrates) to be sure your changes are maintaining the KH and thus keeping the water stable. Normal nitrification eats a bit of KH, so it will decrease (along with tank pH) over time if your partials are not sufficient.

The reading amounts such as dKH refer to water equivalent to water with (17.86 x 5.4) mg/l CaCO3. I don't know anyone on the boards and few in the hobby who still use the milliequivalents/liter measure - that is for chemists. There are 17.86 mg/l CaCO3 per degree KH. Calcium carbonate is the standard for reference of this and for GH tests. Just call it KH or dKH and give the 5.4 reading and we'll all know what you mean.

Does that muddy the water enough?

 

[Sumpin'fishy]

Thanks for the info, according to his article (link you gave), I have a slightly low buffering ability. What percent of water changes should I do and how often for a heavily planted tank with CO2 added?