Fish do not aggro.
Phomiuna Aqueducts/Maps - FFXIclopedia - a Wikia Gaming wiki
Look at Map 2:
Look at G-8. I charm there all the time. There's a slime in the hallway of G-8/H-8. Enough room to run and lose aggro once you've charmed. Make sure you're at maximum distance from it.
Takes a few practice to do it, but easy once you get it down. Then I head over to the West to fight Fomors.