When we dosed our whole tank, I used a large dog breed pill and split it up to the approx. size we would need for our 125. I did overdose a bit on purpose. If I remember correctly a large pill will treat up to 300 gals? It's been a while... Anyway, I left the treatment in for 48 hours before doing a water change and repeated the treatment 3 times, once a week. We lost our cleaner shrimp, some pods and our sleeper banded goby. I would see if someone could hold onto your goby/shrimp pair for a month while you do the treatment or setup a separate tank for them. The goby I had appeared to go blind by the treatment because it didn't eat afterward and died of starvation. All other fish (including a mandarin) snails, starfish, etc. lived.
I now quarentine and treat all new corals in interceptor (3 treatments each lasting 24-48 hours once a week) and watch closely for other pests before they go into the display. We have a couple dips for flatworms too.