Rotating Drum Filters

Filtering Your Aquarium Water

What Is It?

A rotating drum filter consists of a cylinder of highly porous material which is set to turn as a paddle wheel with only one edge exposed to water at any time. This provides an oxygen rich filtration environment.

How Does It Work?

Water is either sprayed over the rotating drum, or passed under it, causing the drum to spin. As the rotating drum spins through the water, the fibrous material of the drum picks up water. Nitrifying bacteria living in this material can then process the ammonia and Nitrite in the water into Nitrate. Because the bacteria are exposed to air, they have access to more oxygen than their water dwelling cousins, and can therefore process more Nitrite and ammonia, and they can process it faster.

What Maintenance Does It Require?

Ideally, rotating drum filters require almost no maintenance. As with many filters there is an associated pump which must be kept in good working order through regular cleaning. Some rotating drum filters are mounted as integral components in a power filter, in which case, the power filter will require normal maintenance. Also, any tubing associated with the rotating drum filter will need to be kept clear of debris and waste to ensure sufficient water flow through the system. You will also need to make sure that your drum is not spinning fast enough to throw water, the water should smoothly flow past or over or under the rotating drum without any spray or splashing.

What Should I Be Aware Of?

Rotating drum filters often stop rotating - because the water level gets too high or too low, because the spray bar or tubing leading to it gets clogged or moved, or because some piece of debris prevents the drum from rotating. If the drum quits rotating, the part of the drum out of the water will dry up, and the Nitrifying bacteria in that part will die. This will reduce the filtration capacity of the filter until the drum is started again and bacteria propagates into the section that had dried out. Unfortunately, when part of the drum is dry and other parts are wet, the drum is off balance, and may not start rotating again freely. At this point, the drum may have to be replaced.

Because the drum is mostly out of the water, the filter will cause a substantial amount of evaporation. This could be potentially harmful to your fish, as topping off the tank increases mineral content and hardness. Make sure to always remove water from the tank before topping it off.

Also, because the drum needs to mount over the back of the tank, you will need to provide an opening in the back of the tank cover. This opening will provide a potential escape route for any jumping fish, amphibians, or crustaceans you are keeping in your aquarium.

As the rotating drum collects debris and bacteria, the small openings in the fabric the drum is constructed of become clogged, and no longer allow water to pass through the filter, but instead just to pass over it or bounce off. This can greatly reduce the usable surface area of the filter, reducing the space available for Nitrifying bacteria, and, in turn, reducing the effectiveness of the filter. As these pores become plugged, you can rapidly eliminate the filtration provided by a rotating drum.

Rotating drum filters, when working, provide biological filtration. Because of the many problems with rotating drum filters, many quality pet stores do not carry them.

My snail mail address is: Keith Seyffarth, 217 W. Koch, #308, Bozeman, MT 59715.
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Page most recently modified: November 26 2006 18:35:43.