Since my name, and prior conversations, are being brought up on this thread, let me see if I can add a little clarity to the discussion. Here are a few points of clarification:
1) The true Balling Part C is NOT meant to "make up" for ANY trace elements consumed during calcification. It is used to "offset" or "ionically balance" the NaCl that is left over, as a bi-product, after adding the Parts A & B. Technically, you are "adding" Mg and trace elements, to the system, with the Part C. But you are NOT supplementing for used Mg and trace elements with the Part C.
2) If a salt mixture (ANY salt mixture) contains NSL (natural sea water levels) of trace elements in it, and you do a 10% water change, then, on the one day you do the water change, you will "replenish" 10% of what has been depleted. If you do a 25% water change, then you will replenish 25% of what has been depleted, on that single day! This is math and chemistry, not supposition. The only way to make up for 100% of what is in depletion, with a salt mix that has NSL of trace elements, is to do a 100% water change. You can argue the point of whether it is necessary to replace 100% of the trace elements in depletion all day long. But you can't argue with the math/chemistry of the replacement numbers. This has nothing to do with "rate of usage". It is true for ANY depleted concentrations.
3) Now on a more Tropic Marin brand topic (sorry) ... When we talk about the 17 trace elements that get depleted in most reef systems. We are talking about the 17 trace elements that have been shown to go down in most, if not all, reef tanks. The depletion of these 17 traces is well documented in research. I apologize for not having that specific research reference right at hand. I will try to track it down and post it as soon as I have it. It is our approach that if we know that these 17 traces will definitely be depleted, it probably makes good sense to replenish a small amount of those 17.
I hope this post helps to clarify some of the points that seem less understood on these topics. If not, I am always available, in our office, for a phone conversation to explain about them in more detail. You can get our office phone number and hours on the US Tropic Marin website at this link:
to the website for Tropic Marin USA
www.tropicmarin-usa.com