yellowtail I use fresh garlic also. Is it possible that your goby is just "intimidated" by the others---my firefish were b/c of my clowns and I would have to distract the clowns and kinda spot feed the firefish.
I completely forgot about Koylic and McCormick's, haven't seen that mentioned in a long time.
hagfish and Magic Just cut up a clove into a few pieces (I don't crushed it) add to the cup with tankwater and the food and let soak. I use tongs to remove before adding, you could strain or whatever you chose. I never added the garlic to the tank, just the food that has absorbed the juices.
I only feed them this way once a week. Yes, it is said to build immunity to ick (or is it ich), but IMO too much can cause an immunity to the garlic. My 2 cents. HTH