Fish tank filter

Claim 1

A filtering device, particularly for use in filtering aquarium water comprising: a tank having an inlet, outlet and intervening communication chambers; filtering means within each chamber in intercepting relation to the flow of contaminants and water from the inlet to the outlet chambers; said chambers being defined by baffles arranged to provide a labyrinthian flow path between said chambers; a first of said baffles being spaced from the bottom of the tank and a second of said baffles extending from the bottom and terminating short of the top of the tank, whereby the water is caused to flow beneath said first baffles and over the second baffles, said chambers having bottom portion and said filtering means filling said bottom portion above the lower ends of the first baffles and below the upper ends of the second baffles; indicia means supported in said tank and operative to indicate sludging conditions in said flitering means, said indicia means comprising a vertically slidable element mounted within the inlet chamber and having means for adjusting the draft thereof, and said element slidably supported against an associated baffle, and means for guiding said element along said associated baffle, and an envelope on said element having means for sealing and opening the same.