This wasn’t an incident with my fish tank. It was for all fish tanks in Los Angeles. You didn’t have to treat tap water until a couple of decades ago when it was announced in a mailer to all DWP customers that the water was no longer safe to go directly into fish tanks. Maybe this is apples and oranges with fluoride vs. chloramine, but I associated it with fluoridation at the time. (Either way if it isn’t safe for freshwater fish? Canary. Coalmine.)
I’ve had fish up and down the west coast. With flouridated water. I always gave water a chlorine rest, and never had an issue.
I’m also (or used to be) an amateur koi raiser. Water quality is extremely important, but in all my days talking to other owners and enthusiasts have I ever heard flouridation brought up once. Nitrates, salt, fungus, iron, and a million other things. But never flouride.
