Im pretty new to dosing myself, i always did multiple water changes a week but its getting old. From reading and speaking with others i have gained somewhat of an understanding which is still foggy.
Anyways, there is actually no problem dosing more of one than another in a reef. All tanks like you said are different. Volume, livestock choices and coraline algae obviously play a major role in usage.
When your levels are not in check you have have different things happening that will throw off your levels even more.
The idea with a reef is to test and dose for around 2 weeks while adjusting to keep your levels in check. I shoot for 8.5 alk, 430-450 cal, and 1300 mag. Once you get these levels you should test, do not dose for 24 hours and test again. Then see your results. You should be able to recognize your usage. If not, repeat. These test kits can be finiky and and testing experience helps recognize levels. Always test the same time, I test in the evening and split my doses up to an am and pm dose.
I personally check levels and only visually see a change in my alk. Calcium always looks the same to me daily but if i dont dose i can watch it go out of wack with 2-3 days. So, I still dose the same amount for both alk and cal and everything has been great.
If your alk is dropping and you really don't really see a change in calcium then dose equal amounts of both alk and calcium. Then start weekly checking levels and watching your livestock. If you see any change like calcium getting to high etc then you can start adjusting.
Make sense?
If your dosing esv like I am you can see that you need to dose approximately 1ml per gallon to raise alk 2.8 dkh an 1 ml per gallon to raise calcium 15 ppt.
If your dosing 30 ml on your tank of alk follow it with a 30 ml of calcium. You should be dosing each in flow and should be waiting in between both doses.
I generally use to keep my mag in check with weekly water changes. You could probably get away with weekly doses or water changes to replenish if your doing a mixed reef.
