Ionic silver as an ich treatment?

[425nm]

For the love of your fish/coral STOP dosing a heavy metal that you can't measure!!

Silver is definitely toxic to freshwater fish (it inhibits the Na+/K+ and ATPase used by the gills in osmoregulation) and is probably toxic to marine fish let alone invertes.
On top of this its toxic at the range of 0.01-0.17MICROGRAMS/L of water. You can very very easily hit that level without realizing.

If you can't quantify it, don't put it in your tank (or your body).
Edit: I'm sure there's a good chance that it'll kill ich but also lots of other things in your tank.