FWIW, one can't give a final magnesium concentration target if it is an impurity in Tech M that is active, because tanks start at such different magnesium levels and it presumably is the rise that is important, not the final value.
Randy,
Not to argue with you, but the magnesium concentration you are at with Tech M is also an indirect indicator of the trace element concentration in the Tech M that is killing the Bryopsis. I would think the concentration of the impurity (trace element) and the exposure time to that trace concentration could be just as important as the rise in the trace concentration. As the actual element in the Tech M killing the Bryopsis is unknown, the magnesium levels obtained using Tech M would seem to be the best method to have some type of quantitative treatment protocol.
Mysterybox is a friend of mine from our local reef club, so I have no doubt as to his experience, but Tech M killed all my bryopsis. My method was to use Tech M as the sole means to raise the Magnesium levels from whatever concentration it was initially, take the magnesium level up to 1800, then maintain it there with Tech M for a period of two weeks.
Anecdotally, from all the threads I have read, etc., many of the cases where folks use Tech M, but fail, is related to not using Tech M as the sole method to raise the Mag levels of the tank. Instead, they use Mag sulfate or your 2 part formula to raise the mag. levels, then add Tech M when mag levels get to 1600 or so, thereby reducing the concentration and exposure time of the bryopsis to the trace in the Tech M that kills it.
Alternatively, some folks use Tech M solely to raise mag levels, but don't maintain the 1600-1800 magnesium levels in their tank for long enough for a complete kill of the bryopsis.
Regardless of initial magnesium concentrations, the success stories you read about have folks using Tech M to get to mag levels of 1600-1800 and they have a two week period of time they keep it at those levels. Many of my local reef club members have used this protocol with success.
This is, of course, not written in stone. I'm sure trace levels can vary in Tech M according to the batch, and there may be some Bryopsis species that react differently to Tech M than others.
The original Tech M labels listed 24 different trace elements. I've always suspected is was copper, since copper is used as a FW algaecide in ponds, but that is just my personal opinion.
For readers of this thread, here is the list of ionic trace elements in Tech M:
Deionized water containing the following elements (as ions): magnesium, chlorine, sulfur, calcium, potassium, bromine, strontium, boron, fluorine, lithium, rubidium, iodine, iron, molybdenum, zinc, nickel, copper, manganese, vanadium, cesium, cobalt, tungsten, selenium, and chromium.
Also, I am sure there are other ways to kill bryopsis than Tech M, like the H2O2 method Mysterybox used. Tech M is a fairly user friendly, but expensive way to do it, with most folks using it successfully.
Dave
