i seem to agree with drummereef quite often. he's right--never add anything you can't test for. the only thing that i would point out is that the two part supplement he suggests will also raise your SG. so keep that in mind when doing water changes. it seems that 90% of reefers on here will only dose calcium and alk. i also add magnesium, iodine and strontium, but i also think that you should start by simply adding alk and calcium for now and perhaps for ever. and yes, the other elements are generally replaced with weekly water changes.