Why haven't I seen my corydora eat yet?

I have this half inch albino one(yeah i know i should have 5 or 6, I'm getting more later this week) and I've NEVER once seen him eat. I've had him for two months though and one time he was bloated so i guess he must eat... But he eats NOTHING i feed him. At first i tried sinking shrimp pellets but before they sank the other fish went crazy and eat them. and the ones that did sink got eaten by the platies and ignored by the catfish. someone said they eat particles found on the bottom. Is this true?