For my Ich problem, I have been dosing my tank with garlic drops and putting in the food. Ginger seems like it would do the same thing, boost the immune system of the fish. My corals have not reacted to it in any way. In addition, I have been dosing pima and mela fix to help the healing process. They are both derived from natural plant oils. As with any "natural" cure, there are going to be skeptics. I for one think they're worth a shot over some artificial medication. The idea is to keep everything as natural as possible, just like when we get sick. Haven't your grandmothers told you to drink lots of orange juice to fight a cold. The vitamin c in oj will help your immune system....on the same note, aryuvedic medicine has been parcticed in India and China for centuries. They have all kinds of "cures" that we would think are crazy. But now look how many people incorporate ginseng and other roots in their diets!
Either way, it is not correct to say there is a cure for anything, everyone has different results. We should however use this forum to help fellow aquarists with any of our own experiences...which means I will be trying ginger in my next feeding.
Good luck, ich sucks.