The invention relates to the technical field of breeding devices, particularly to a fish tank with a filter unit. The fish tank with the filter unit comprises a square tank body, the left of the inside of the tank body is vertically provided with a water baffle, and the right space enclosed by the water baffle and the tank body serves as a filter area; a filter plate is arranged above the filter area, and a layer of sponge is laid onto the filter plate; a water collecting box is arranged under the filter plate and on the right of the water baffle, the top of the water collecting box is open, the right of the bottom surface of the water collecting box is provided with a diversion port, and an overflow port is formed between the water collecting box and the water baffle; filter gravel is paved at the bottom of the filter area; the top of the water baffle is provided with a filter plate overflow port, the part of the water baffle, which is arranged between the filter plate and the water collecting box, is provided with a filter gravel overflow port, and the bottom of the water baffle is provided with a filter-out port. According to the fish tank with the filter unit, a user can at any time observe whether the fish tank needs cleaning or filter medium replacement and can conveniently disassemble the fish tank during filter medium replacement, thereby reducing the burden on cleaning a fish tank filter.