Man I guess I didn't know how lucky I was. The guy who mentioned this to me has quite a background. Also has many colleagues to help answer questions.
He said that magnesium was the easiest 'macro' deficiency to induce and its very easy for the plant to rectify.
He also said this during one discussion about nutrients.
'Because I come from a scientific back-ground in botany and horticulture, and I've worked for ~20 years in a lab. where we did a lot of work in ecology and phytoremediation, I think I've probably got more understanding of the principles that under-pin much of what happens in the aquarium than the average fish keeper.
The other great advantage I have is that I work in the same school with statisticians, animal ecologists, plant physiologists, micro-biologists, plant ecologists and analytical chemists, so I when I don't understand something I can always ask a colleague.
For example when an analytical chemist with 35 years experience, in a lab. with ~£500,000's of pounds worth of kit, tells you it is quite difficult to measure some anions (like NO3-) accurately, you tend to take their word for it'
Doesn't make it so but this is why I tend to take the API test with a certain degree of scepticism ☺
