Your filter should remain on at all times. Your aquarium needs continuous filtration, and running your filter at all times is the best way to do that. Before adding any fish to your tank, it’s a good idea to run your filter for at least 24 hours so that some good bacteria can build up throughout the filter and the tank’s water for your new friends.
Sometimes, your filter may turn off if there’s something wrong with it, or maybe it will seem like it’s not working because it’s clogged. This means you need to clean or figure out how to fix the problem. Worse comes to worst; you may need to buy a new one. However, filters are pretty sturdy and will last you a few years. If the power goes out in your home and the filter doesn’t work for a few hours, it’ll be okay. However, it should always be running.