Yeah I think you gave us the answer ... You keep adding food.
I know it sounds simple but just feed less. If they don't eat it in 2 minutes they're not hungry enough.
That being said I swear by New Life Spectrum Thera A. I've had this container for over a year and only used half in a 29 gallon. The garlic maybe attracts them ... They turn their nose up at frozen food.
Sent from my iPhone with three hands tied behind my back.