Bubble counter liquid

So I'm researching setting up my calcium reactor and on one article, it mentioned using special bubble counter liquid which is thicker than water and supposed to resist evaporation.   My question is, for those of you using calcium reactors, is this really necessary?  If you don't use this special liquid, what kind of evaporation rates do you see inside your bubble counter? 
--AJ

 

Thanks for the feedback guys....that helps. The evaporation rates you describe are actually higher than I would have thought considering that it's a sealed container and there's not much CO2 passing thru it.

--AJ