Then take up your cause and go search phosfree and post this so people like me do not get bad advice
Exactly. That is precisely why I am posting warnings here.
Some organisms are far more resistant to zinc than others, some by a factor of 100 or more. For most, the longer the exposure, the stronger is the effect. Some effects take many days to show up. If you loose one of those "shrimp" you saw a week from now, will you attribute it to the additive? Will you even notice?
The problem with a comment like "it worked for me" is that it may be exclusive to your tank system and the creatures you keep, and yet new reef keepers may not recognize the dangers that are obvious to folks who are familiar with the scientific papers on the subject. In fact, you have few of the sorts of organisms that are most sensitive. Fish are fairly insensitive.
The toxicity of zinc to marine invertebrates is not a matter of opinion. It is a clearly established scientific fact, and you can pull up many free pdfs online which show exactly how much causes what effects, and which show that you likely dosed more than the safe limit, even when "starting slowly".