As mentioned before, I found that running a reactor with Carib-Sea media, kept strontium, calcium and magnesium levels at proper levels. Besides that or the mixtures I now use, I also found the two parts to do the same. Both ESV,s B-Ionic and Two Little Fishies C-Balance. Although I have not used them much or measured results, I would expect the same from Seachem.
Now my take on trace elements, {which I dont consider the above,
}. For years I used Two Little Fishies Combisan. There are many of us that have sworn by it, despite the research on RDO or where ever it was that said it was 99% water. As some of us posted there, then the remaining 1% muct be powerful.
As seen in my previous TOTM tank and from all the soft corals I rasied in the 90,s and sold, they were large and great looking. Was it partially because of the Combisan use, who knows? I always thought I could see a growth and colour difference when using it or not using it.
I figured besides what else was in there, the iron, {which several aquarists now use} and the iodide was helping the soft coral growth. I dont use it anymore. Maybe thats why my corals never look the same anymore.
Just my take, FWIW, as a point of discussion.
I have also used ESV Iodine. I found that when added and my levels came back up to the required .08ppm or whatever it was, a couple days later it was back to 0 ppm. Or at least thats what the test kit showed. Salifert or LaMotte, I cant remember.
There was a big hassle on RC regarding its use and the measure of it.
But what else is new.
I would guess besides all this, regular water changes would maintain these levels, {has anyone measured trace elements in new saltwater??}. But when the salt mix was much more expensive and/or in larger tanks, I found that not the best route.