Instructions
Check the condition and operation of the filter to determine whether or not it is working properly. If no water is flowing from your power filter, it is not working right. Unplug the filter and plug it back in, then fill the back of the filter with water. If the filter still does not start it should be replaced.
Remove the old filter carefully from the aquarium. Keep a bucket nearby and immediately place the filter in the bucket to avoid dropping water on to the floor. Discard the old filter.
Purchase a filter that is designed for a larger tank than the one you actually own. This helps the filter keep the tank clean without straining its motor. For instance, if you have a 20-gallon tank you might choose a filter designed for a 30-gallon aquarium.
Put the new filter in place and insert a new filter cartridge. It is a good idea to buy several replacement cartridges when you buy the filter and store them in your aquarium stand.
Fill the back of the filter with water when using a power filter designed to hang outside the tank. Attach the aquarium tubing firmly when using a filter that goes inside the tank. Plug the power filter to an electrical outlet, or the inside filter to the aquarium pump. Watch the power filter to make sure water is flowing back into the tank. Check for bubbles coming out of the inside filter.
How to Replace an Aquarium Filter
No matter what the size of your aquarium, the filter plays a vital role in the health and well-being of your fish. Changing the filter cartridges should be a regular part of your tank maintenance. For most filters that means changing the filter at least once a month, and checking the filter every time you do a water change. If you find that your filter is not working properly, the malfunctioning filter should be changed right away.