I got some plain ole calcium today, so no need to mess with the Kalk now. :D

I don't test pH because it's not overly important, like testing nitrite. If everything else is on target, and I'm using a skimmer it's impossible for pH to be so out of whack that it will affect anything.

I got the pH pen today, but it's calibrated with pH 4 and 7 fluid for freshwater, so I need to get some pH 7 and 10 calibration fluid for saltwater.

For what its worth, I use a 2L juice jug, add several tablespoons of kalk, add water, let sit for 1 hour at least, pour the semi-clear solution into the sump but not the concentrated slurry on the bottom.

I do this several times a day into my 210g with 75g sump with no problems & good coral growth in a heavily stocked (both corals & fish) display with a high calcium requirement.

On some of the sps, am achieving at least a cm/month growth.

Anthony