I fed mine daily in the evening. They take almost everything, like frosted Artemia, Daphnia, mosquito larvaes and Mysis. You can also give them crushed tablets or any other dry food, but they do better with frosted. Even living food gets accepted.
I don´t keep mine anymore. I collected the specimens myself and only kept them for a few months, but they were about 2 inches too. As I said, they will take pellets as well, but they shouldn´t be to big for their mouth. Good luck with them! Imparfinis are really adorable. Active and easy to observe.