Confused about dosing

[Topher38]

Been paying attention lately and new to dosing I'm using (it seems) .1dkh/day 60ppm cal, and 30ppm mag/day.
Last night I dosed alk(seachem carbonate) to bump it the .1 and a few hours later I dosed cal (auquavitro calcification) 15ml (tank is a 29g) and 50ml of mag (Randy's recipe with Epsom salt, and the other salt)

This morning I tested my alk it was 7.8-7.9 can't remember. What's going on?

 

[PatW]

Well that is strange. First off, to deplete Ca, ALK or Mg, you need something that forms calcium carbonate: Hard corals, clams or snails.

It is my impression that ALK varies the most. Depletion of ALK can cause bad things so I watch it carefully. If you read stuff by people who raise SPS corals, they routinely measure ALK daily.

In your case, you had Calcium go from 460 to 400 in a single day. I does equal amounts of ALK and Calcium (2 part). I measure ALK daily and I dose daily. And I often see a .1, .2, .3 move in DKH in a day. I dose Calcium but I measure just every so often (like once per week). I shoot for 450 and sometimes it will get down to 420 in a week. I have never seen the kind of move you are seeing. And for Magnesium, it stays constant and I measure rarely. Water changes seem to keep it stable. I understand that when corals grow, they take up Mg in far lower quantities than Ca and ALK. By the way, my tank is SPS. Dominant.

Looking at your results, I would think it looks like a testing error. If I saw that kind of change in Calcium in one day, that would be my conclusion and the same for Magnesium.

If anybody knows something that would cause your observed results, Randy would know it.