A healthy, adult betta fish can go without food for about 5 to 14 days. Under extreme conditions, some betta fish have been known to survive for up to a month without eating, but this is not recommended and can lead to health problems.
When bettas are in a healthy environment, they should be fed daily or every other day. Bettas are carnivorous and need a diet that is high in protein. They thrive on a diverse diet of high-quality flakes, pellets, frozen, and live food intended for bettas. The amount to feed them depends on their size, but bettas typically only eat an amount that is about the size of their eye.
While a betta can last for a period without food, it is important that it doesn't become a habit as it can lead to health complications. Starvation can lead to their organs shutting down and even death. It can also weaken their immune system, making them prone to diseases.
If you know in advance that you will be away and unable to feed your betta, there are automatic fish feeders and vacation fish food blocks available on the market. These can ensure that your fish is still being fed even when you're away.
However, it's important to use these options wisely. Automatic feeders can sometimes dispense too much food at a time, which can lead to constipation, obesity, or a mucky tank if the food is not eaten. Vacation food blocks can alter the chemistry of the water, potentially turning the water acidic or alkaline, which can stress your betta out.
The best approach would be to have someone responsible to take care of the fishes and feed them in your absence. When this is not possible, resort to other methods but be sure to thoroughly research and apply caution.
In conclusion, although bettas can survive without food for around two weeks, their health and happiness will suffer. It is crucial to feed your betta regularly to keep them healthy and vibrant. Avoid long periods of starvation to prevent risk of malnutrition and other health complications.