Fish, like any other creature, need proper nourishment to survive. However, how long they can survive without food varies greatly depending on the type of fish, their size, and overall health.
Typically, most common pet fish species can last for anywhere between 2-10 days without food without enduring significant harm. Factors that allow them to survive this period include their lethargic physiology and slower metabolic activity, which helps conserve energy when food is rare. Additionally, they can also nibble on algae and other organisms in the tank for supplemental nutrition, if available.
But it's crucial to note that the survival period may vary. Species like goldfish are notorious for overeating, but they can also withstand approximately eight days without food due to their slow digestion system. Bettas, on the other hand, can live for up to two weeks without being fed because of their ability to store and metabolize fat reserves effectively.
Then there are some types like the loach and pleco, which can survive even longer periods without feeding since they're bottom feeders and can live off the debris and algae in the tank. Similarly, fish in the wild can survive for longer durations without eating because they have more access to other natural sources of food, apart from the standard feed.
Notwithstanding, enduring these maximum periods without food is not ideal for your fish since it places them under great stress, which decreases their immunity and makes them vulnerable to diseases. Also, it can lead to a reduction in growth rate, physical deformities, poor coloration, and terrible breeding capacity. Hence, maintaining a regular feeding schedule is essential to keep them in optimal health.
Fish owners who need to leave their fish for an extended period should consider automatic fish feeders, which can dispense food at preset intervals. Another option could be slow-release feeders that gradually let out small amounts of food over a set period, usually a few days.
To summarize, although fish can survive without food for quite a few days, consistently providing them proper nutrition is crucial for their wellbeing. If there is a necessity to leave them unsupervised for an extended period, automated feeders are an excellent way to ensure they're fed regularly.