It is perfectly normal for your FH to not eat after being moved to a new tank, Kapatid. There is actually no need for medication. Although FHs are known to be adaptable fishes, some actually take days or weeks to adjust to their new environment. If ever he doesn't eat, don't you worry, FHs are hardy fishes. There is one instant in this site where a member's fish has not eaten for 2 weeks, but came out alright in the end.

Good luck, Kapatid, and keep us posted!

-Daniel (niel_0515)