Answer: While I don’t have an issue with the practice of occasionally fasting fish, I’m always wary of making any sort of blanket recommendation such as “Marine fish should be fasted every X number of days.” In my opinion, a much better approach is to think in terms of feeding in a manner appropriate to the particular species—which may or may not include fasting.
For instance, some predatory species, such as groupers and moray eels, naturally take in large prey items in one sitting and then go without eating for a relatively long interval until another prey item happens along. With these fish, it may be appropriate to feed only once or a few times per week and then allow them to fast in between meals. On the other hand, zooplanktivores and herbivores (such as anthias and many of the tangs/surgeonfishes respectively) naturally feed frequently, if not continuously, throughout the day.
Thus, in an aquarium setting, it’s appropriate to provide multiple small feedings each day for zooplanktivores and continuous grazing opportunities for herbivores. MORE