During the winter when live food is most challenging to obtain, a staple diet of dried food will need to be given.
Dried shrimp, obtainable in varying grades to suit numerous sizes of fish, will maintain fish in reasonably great health if occasional feeds of raw meat or live food are also given.
Bemax mixed with a dry food is an outstanding food which is rich in vitamins, but if given to smallish fish it should be rubbed via a fine mesh sieve.
There are many brands of prepared dried foods in the marketplace, all of which claim to be the very best. The ingredients that go to make these various foods are numerous, and it is almost impossible to judge the one most suitable for all occasions.
My own technique would be to have a tin of all of the well-known makes, and feed the fish from a various tin every day. This way the fish appreciate a maximum selection of diet.