The only time I feed mine is when I'm checking on them for some reason, or a friend is over and I'm wanting to show off
Mine are several years old and healthy, so they definitely don't NEED the pellets or anything, it's strictly just for me.
I have a koi in an aquarium, though, and I've been feeding him twice a day... 8 pellets in the morning and 24 at night. Which is about how much he'll eat in 5 minutes. I know, I know, I REALLY should move him to the pond, but I worry about him... that's a longer story that's been discussed before, though, and I don't want to hijack the thread with it.