A troubleshooting guide to common problems can be found here: Marineland Emperor 400 Power Filter Troubleshooting
The Emperor 400 is an ideal fish tank filter for any amateur fish tank hobbyist or long-time enthusiast. The Emperor 400, along with its smaller lines of filters, can be identified distinctly by their Bio-Wheel filtration system. The Bio-Wheels are the last of a three stage filter. The first is the initial filter, Rite Size E, which removes all solid material from the water. The provided media cartridges allow you to add activated carbon or improvised media such as %100 polyester pillow stuffing as a secondary filtration stage, followed by the Bio-Wheels, which hold beneficial bacteria for the fish tank. The Emperor 400 is very affordable and reliable, pumping an amazing 400 gallons per hour, with a small power consumption of 19 watts. These filters are extremely reliable, and issues that arise are usually small and due to lack of maintenance. There are other competitor filters on the market that do not have the Bio-Wheel, which is a brilliant edition to a filter. This filter operates extremely quietly, is very easy to get going, and very affordable, which makes it a great filter for anyone into the fish tank hobby.