Use to feed mine small 6" whole pompano. They sold them whole in the frozen fish section at my local grocers for some reason. My big cats loved them. Plus as you say they had everything in tact just as what they would eat in the wild so was great for their growth and coloration.
I use to supplement with shrimp and whole shrimp for the rtc also. Seems to bring out a whole new red in the dorsal and caudal fins.