Very interesting indeed. I like that he emphasizes the relationship between Ca, Mg and
K, how high levels of one can inhibit the uptake of another. I also like how he ultimately suspects the health of the plants is the main deterrent and not toxic levels of Mg, per sae
I doubt that a healthy planted aquarium could be achieved long term with such high Mg vs Ca and K. As he pointed out youd soon run into a faux K deficiency that simply adding more K wont fix (kinda like the "micro-tox" K pinholes Hygros are prone to get)
Personal experience: 10 years ago I was a huge fan of Mg, for all the reasons the author mentioned. The more the better I thought. But this was "book knowledge" an opinion formed on literature, not actual trials and experience. Ive ran as high as 2:3 with Ca, and 1:1 with K. The latter was a disaster but thats another story. I spent the most time with Ca:Mg in the 2:1-3:1 range (~5 years)
Plants did well at that level, obviously more was involved in that than just the Mg ratio, but it was a solid ratio to keep. Then I started backing down Mg. Using less slowly over time, for no specific reason. I never saw an adverse response to using less and less Mg. Fast forward 3-4 more years, Id stopped adding any extra at all to my tap water, which comes with about 35 Ca and 5 Mg. Ive been able to tell literally no difference and thats what I still run today
Take that for whatever its worth. Its just what Ive seen with my own tanks over the years growing about every plant we have in the hobby. I will also add that at no time was I running controlled Mg experiments. Its just what wound up happening. Was there ever a time when plant X was doing bad and adding another 5 Mg would help? Idk, its entirely possible. I did try that a couple different times, esp early on when Id first gotten back down to tap water levels. It didnt fix anything, but admittedly I havent proven beyond a doubt that having more wouldnt help...something
