IMHO feeding fish at night is a convenience..unless you work shifts
but yes, it is recommended to feed nocturnal fish in the evening or at night becoz at this time of the day their metabolism is highest. if you put in food during the day, it will eat but not much, and the water will dirty very fast. my two cents. all my catfishes and plecos feed in the evening. i don't feed them during the day although my plecos will eat anyway in front of me.