Ugh, I can't stand it when people do this and don't realize they are causing a living creature real pain (and potential death)... my sister had a betta and asked her roommate's brother to feed it while she and her roommate were away, since he was taking care of their cat too. When she got back, the entire bowl was murky and full of flakes, her fish had suffocated, and the entire room reeked of moldy food and dead fish. I don't remember if he had accidentally knocked all the food in or just didn't want to feed it every day so he fed it what he thought would last for a week, but either way, it was awful.
I'm really glad you were able to take care of Perry!
If I lived in Ponyville, I'm pretty sure my cutie mark would be a taco.