Instructions
Under Gravel Filter
Take out all gravel, fish and decorations from your tank. If this is a new tank, install the filter before adding any of these other things.
Place the under gravel filter that is appropriately sized for your tank in the bottom of the tank with the riser tubes sticking up near the top of the tank.
Cover the bottom of the tank with 1 to 2 inches of aquarium gravel.
Slide air stones down the riser tubes so that bubbles rise up inside the tube. This causes water to be drawn through the gravel and out the riser tubes, filtering the waste out through the gravel. This can also be achieved using an actual pump, which results in a higher flow rate.
Clean your gravel once a week with a gravel-vac so it can properly act as a filter. The slow moving water over the gravel also allows large amounts of beneficial bacteria to grow on the gravel so you receive some of the benefits of a bio-wheel without the expense.
Hang-On Filter
Choose a filter that is appropriately sized for your tank, and is large enough to filter your entire tank five times per hour. For example, use a 100-gallon-per-hour filter with a 20-gallon tank.
Remove the filter from the box and assemble it per the instructions included with it. Usually you only have to place the filter media inside it and attach the water pick-up tube.
Hang the filter on the aquarium so that the bottom water pick-up tube is submerged.
Plug the filter in and check that it is properly pumping water through.
Canister Filters
Purchase a canister system that is powerful enough to handle the amount of water in your aquarium.
Set the canister underneath your tank or hang smaller ones on the tank.
Attach the plumbing to the canister so that you have and "in" and "out" hose.
Put the hose that sucks water into the canister at about mid-depth on one side of the aquarium.
Fasten the output hose for passing the filtered water so it is just above the surface of the water on the other side of the tank. This allows you the option of adding a bio-wheel at the end of this hose for better biological filtration.
Affix a bio wheel underneath the outlet tube if you desire the biological filtration it provides.
Power up the filter and check that water is properly flowing out the outlet.
How to Install a Fish Tank Filtration System
Some fish tank filtration systems go under the gravel, some hang on the tank and others are completely sealed and kept separate from your aquarium. Each has its own benefits, but they all do basically the same thing. After deciding which option works for you, follow a few simple steps to install your aquarium filter.