I wanted to post a follow-up... In my third game (out of five) I finally bed my last Magic Fish, but at the same time two of the tanks had many sick fish (despite the fact that the "nursery" now had several Magic Fish of Healing!)

I collected all of the sick fish together in one tank, and it took three doses of the Ick treatment, and 9 doses of the fungal treatmeant to cure them all. That would have taken several hours if I had to wait a 1/2 hour between each dose! Thanks again for the tip!

Now I have another question:

Can you drop the medicine into the isolation tank? I'm thinking that if you have only one sick fish left, it might be easier to to find the "sweet" spot that way.

(I'll try it myself the next time I have a lone sick fish.)