It works like a regular sponge filter that is driven by an air pump. The difference with this particular filter is that it has two media cups that can be used for bio media. The advantage of having the bio media is in case you over rinse the sponges you should still have plenty of good bacteria within the cups.
I like to pull half of the bio media out of the cups of an existing filter and use it to seed a new filter greatly reducing the time it takes to cycle a new tank.
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