Goldfish should be easy...mine were such a pig when I had them. I never even considered handfeeding Plecos, they dont seem like the type. Stick your hand end whenever you drop food in there, soon they will associate your hand with food and start coming up. You can use frozen cubes of food that they like (blood worms, etc) and theyll come pick it off. Most of the time, it just takes time for your fish to be comfortable with you and they'll come and nip your fingers when you stick your hand in,