I thought that to Floyd (I do not disagree with you at all but, I would like to share my findings. I was even afraid to use the lime water AKA KALK. I happen to hold your advice in very HIGH regard Floyd.), so, I did some investigating. Granted it was not super duper thorough but, this is what I found. Take this place for instance http://www.gettankedaquariums.com/in...Main.Page..htm . They have calcium chloride that is only 94-97% pure. The stuff I got at my local pool supply was only .05% impurity which was labeled as chloride??? I figured it had to be OK. Its so concentrated in the first place that you do not need much. I mixed 1.25 cups to a gallon. Approximately One Liter of this mix raised my 40g Ca a lot, it was around 200PPM increase or so. I didn't get a 100% check on the first test as it was in the area of 150PPM, yes very low. After 1L of Ca mix dripped in it went to 350PPM. I figured most of the time I will be using the KALK and only using the Ca chloride for adjustments when the ALK is to high to dose KALK. Any other experience or data on this would be very appreciated as in the past I have always bought the bottled pre-packaged dosing stuff from the SW supply outlets. So please any input would be great.