If adding kalk
you definately need to test for alkalinity as well as the Ca
test you already have. Alk
need to be >>balanced
is not the same as KH
measures the combined parts of Ca
and magnesium and does not need to be tested in a SW
or mEq/l CaCO3
equivalents) measures the total amount of hardness within the system and is very important.
Strontium is rarely a needed addition and simple water changes will take care of that. Nothing in your system will require it's addition. If nothing else, get a test kit to monitor the levels. If Sr gets too high it can be a problem and will actually interfer with certain test kits such as Mg
Iodine is another not really needed addition unless you have animals/algaes in the tank sucking it up in large numbers. As before, be sure you are testing for it. Most tanks don't need it or at least much less than you think.
I would also suggest you get a pH test as well. Mg
can be an important component of the chemistry but is easily maintained with regular water changes. If you ever have issues maintaining the balance between alk
you may need that as well.