the worms are scavengers and will love oat, or cereal, or cornflakes.
Only thing that could be a con would be , that some food you feed to the worms may cloud your water more than others.
Feeding white bread is fe worst than feeding crushed pellets.
You just have to try.
The cloudiness will be gone in no timewhen your filters are working properly.
I sometimes feed the pupae to my fish, for they love those as well.
When i fed white bread my tank will become a "snowglobe" within minutes.
You do not want to feed those when you intend to sit and watch your fish for some time.