Oliver,
Don't worry ... they will survive if you feed them.
I feed mine a mix of cycloeeze, ground up flake food, mashed up pellets, Selcon, and Spirulina powder.
I've had mine grab pellets before and try to eat them, so play around with some of the foods and see if you can get them to take it. The most important thing with feeding them is not to blast them with any hard current if your doing the feeding tube method as the will cause them to retract