Water purifying device and method of aquarium

The invention provides a water purifying device of an aquarium. The device comprises an aerobic thermopnore and a dynamic membrane bioreactor connected with the aerobic thermopnore. The invention also provides a water purifying method of the aquarium. The method comprises the following steps of: feeding the to-be-processed water in the aquarium into the aerobic thermopnore for a reaction; and feeding effluent after the reaction into the dynamic membrane bioreactor for filteration and enabling the effluent to flow back to the aquarium. The water purifying device of the aquarium is simple in structure, good in fluid mixing performance, high in sludge concentration and strong in shock resistance, can be used for effectively purifying the polluted water in the aquarium, is beneficial to the health growth of fishes and ensues that the COD (chemical oxygen demand) removal rate is greater than 88%, the ammonia nitrogen removal rate is greater than 90% and the nitrite removal rate is greater than 92%; the device needs no regeneration and can operate stably for a long period; and the device is simple in use method and lower in cost.