A filtering device configured to draw water from an aquarium and the like and circulate the water inside said device, said device comprising: a container comprising a first housing portion and a second housing portion containing a flow control device and placed adjacent to the first housing portion, the first housing portion having a first inlet made between the first housing portion and the second housing portion in a lower position and a second inlet made between the first housing portion and the second housing portion in an upper position configured to allow the entry of water taken from said aquarium into said first housing portion, a discharge outlet connected to a discharge duct being made in the second housing portion below the first inlet, the first housing portion containing at least one filter in order to filter water, the flow control device having an entry for taking water from said aquarium; wherein said flow control device has two operating positions, a first operating position and a second operating position, the first operating position being a filtering position and the second operating position being a cleaning or backwash position; wherein, in the first operating position of the flow control device, said entry is in communication with said first inlet, so that water taken from said aquarium is put into said first housing portion through said first inlet, passed through said first housing portion, filtered and then put back into the aquarium, wherein the discharge outlet is closed, the first lower inlet is opened and the second upper inlet is closed, so that water to be filtered is taken from the aquarium, sent into said second portion and then, through said first lower inlet, sent into said first portion while rising up, is filtered and then put back into the aquarium; wherein, in the second operating position of the flow control device, said entry is in communication with said second inlet, so that water taken from said aquarium is put into said first housing portion through said second inlet, passed through said first housing portion in a direction opposite the direction of water travelling through the first housing portion when the flow device is in the first operating position, thereby reversing the direction of flow of water inside said first housing portion, cleaning the at least one filter before being discharged, wherein said discharge outlet and said first lower inlet are closed but on the side of the first portion they are connected between them, so that water taken from said aquarium is sent into said second housing portion and then, through said second upper inlet, into said first housing portion where it flows down cleaning said at least one filter and, through said lower inlet and said discharge outlet connected with each other, enters into the discharge duct where it is discharged. a container comprising a first housing portion and a second housing portion containing a flow control device and placed adjacent to the first housing portion, the first housing portion having a first inlet made between the first housing portion and the second housing portion in a lower position and a second inlet made between the first housing portion and the second housing portion in an upper position configured to allow the entry of water taken from said aquarium into said first housing portion, a discharge outlet connected to a discharge duct being made in the second housing portion below the first inlet, the first housing portion containing at least one filter in order to filter water, the flow control device having an entry for taking water from said aquarium; wherein said flow control device has two operating positions, a first operating position and a second operating position, the first operating position being a filtering position and the second operating position being a cleaning or backwash position; wherein, in the first operating position of the flow control device, said entry is in communication with said first inlet, so that water taken from said aquarium is put into said first housing portion through said first inlet, passed through said first housing portion, filtered and then put back into the aquarium, wherein the discharge outlet is closed, the first lower inlet is opened and the second upper inlet is closed, so that water to be filtered is taken from the aquarium, sent into said second portion and then, through said first lower inlet, sent into said first portion while rising up, is filtered and then put back into the aquarium; wherein, in the second operating position of the flow control device, said entry is in communication with said second inlet, so that water taken from said aquarium is put into said first housing portion through said second inlet, passed through said first housing portion in a direction opposite the direction of water travelling through the first housing portion when the flow device is in the first operating position, thereby reversing the direction of flow of water inside said first housing portion, cleaning the at least one filter before being discharged, wherein said discharge outlet and said first lower inlet are closed but on the side of the first portion they are connected between them, so that water taken from said aquarium is sent into said second housing portion and then, through said second upper inlet, into said first housing portion where it flows down cleaning said at least one filter and, through said lower inlet and said discharge outlet connected with each other, enters into the discharge duct where it is discharged.