I had one of these eels a few years ago, and in addition to eating krill and shrimp, it definitely ate silversides as well.
Even though Echidna morays are crustacean-eaters it doesn't mean that they won't eat fish. I've seen typical saltwater snowflake eels chase and eat small feeder fish with gusto.
True on it would feed on fish, but yuck on the feeder fish :silly: LOL