IME most products are snake oil and/or most tanks are not in such good balance that the products provide the limiting factor. There is always a limiting factor in how well the livestock will do and few tanks are at the point where trace elements and micronutrients will make a difference.
The real answer is to question anything you buy. Buy it once, use it as directed, then when you run out stop using it. If you see a decline when you stop, keep using it. If you don't see any difference when you stop using it, don't keep wasting your money on it.
