You will want to use distilled white vinegar.
Apple cider vinegar has too many additional carbon compounds & other substances in my opinion. This has been discussed before if you care to search for it.
A 50/50 mix of vodka/vinegar dosed at 4X the vodka only sounds close enough to me. Randy came up with the 7X figure for vodka to vinegar based on the carbon content only. There could be other variables we are unaware of.
I would stick with food grade calcium hydroxide or better, not commercial agricultural products we don't know the contaminate levels of. Randy & I use the BRS calcium hydroxide which is labeled as pharmaceutical grade.
The amount of calcium hydroxide you add will depend on what your purpose is. If you want to increase the output of alk and calcium, you don't need to add vinegar until you have reached saturation of kalk water at 2 teaspoons per gallon rodi water. You can add 15 ml of vinegar per teaspoon of kalk up to about 3 teaspoons of kalk to increase your alk and calcium output by about 1/3.
Randy provides more details here:
What Your Grandmother Never Told You About Lime
http://reefkeeping.com/issues/2005-01/rhf/index.htm
From it:
Vinegar And Limewater To Boost Limewater Potency
Another potentially useful attribute of vinegar is that it can be used to help dissolve additional solid lime into limewater. It does this by reducing the hydroxide concentration in the limewater:
10. CH3OOH � CH3COO- + H+
The H+ combines with OH- in the limewater:
11. H+ + OH- � H2O
The actual dissolution of Ca(OH)2 is limited by the multiplication product of the calcium and hydroxide concentrations in the limewater as shown below:
12. Ca(OH)2 � Ca++ + 2OH-
13. [Ca++] x [OH-] x [OH-] � 5.5 x 10-6
where [Ca++] is the concentration of calcium (in moles/L) and [OH-] is the concentration of hydroxide (in moles/L). Consequently, if you reduce the concentration of OH- via equations (10) and (11), then more Ca(OH)2 can dissolve into solution and still meet the equation (13) requirement.
This would seem like a concern, however, since losing OH- might reduce the amount of alkalinity delivered by the limewater. Luckily, this is not the case. While the OH- is temporarily reduced by the acetic acid in the vinegar, when bacteria metabolize the acetate, they release it back to the water:
14. CH3COO- + 2O2 � 2CO2 + H2O + OH-
Consequently, additional solid lime can be dissolved into limewater using vinegar.
How much can be used? The more vinegar that is used, the lower the pH of both the limewater and the aquarium will be. One reasonable point to shoot for is to add about the same amount of total CO2 via the vinegar as is needed by the lime to form HCO3-. This balance is roughly matched by using three level teaspoons of solid lime per gallon of limewater, and 45 ml of vinegar per gallon of limewater. For those aquarists choosing to use vinegar in limewater, these values are a suitable starting point. Note that the pH of the limewater is still quite high, so slow dosing is usually required.
What kind of vinegar should be used? Luckily, cheap distilled white vinegar is likely the best. More expensive flavored and colored vinegars, such as red wine vinegar, will deliver other unnecessary organic molecules to the aquarium, and are best avoided.
