I have a neighbor who we're friends with trained to feed them.
He comes by, drops a frozen cube in a shot glass, puts in the fridge, and feeds the following night for me.
The problem with automating frozen is that you can't keep it frozen for the week you're gone and it goes to spoil...
Flake, etc, would be ok, but you run the risk of the feeder going haywire and dropping all the food in the tank at once.