What is a roller filter?

Roller filters, also known as fleece filters, are mechanical aquarium filters that trap waste in water flowing through them using a roll of fleece.

As each section of fleece gets brown and dirty it is rolled out of the way and replaced with new. They began as large pond filters, but now their most popular usage by far is as mechanical prefilters for marine tanks

Do they clean themselves automatically?

Some roll the dirty fleece on automatically while others use a manual button or even a handle to wind on the fleece. With automatic models, the only hands-on work is installing them when new and replacing the dirty fleece with a clean one every few months. Manual models involve you giving it a visual check, and then winding the roll-on.  

How do they work?

Manual fleece filters involve two rolls - one containing a large roll of clean fleece and one empty one that the dirty fleece is wound on to. It acts like coffee filter paper, letting clean liquid pass through but trapping the solids on top. Unlike filter socks, you don’t clean the fleece and instead throw away the dirty roll and replace with a new, clean one. 

Automatic roller filters have a float switch inside. The fleece is passed through a box, letting water escape through the fleece but keeping the dirt inside the box. As the fleece gets dirtier and dirtier with particles, the water level in the box starts to rise as the water cant travel through the fleece as easily as it could when it was clean. The water level inside reaches the float switch, which rolls on the filter, and water can flow through the clean section of fleece again. 

Do I need a sump?

At the moment, yes, as the water entering the roller filter escapes through the sides and needs to be caught and recirculated by a vessel like a sump. They don’t have to connect to the drain pipe from your main tank however, and you could connect a powerhead to a hose and hose tail in the sump and have it recirculate in there. Most roller filters are too large to fit into the back filter section of a sump-less All-In-One marine aquarium like a Red Sea Max, but smaller models are coming out in America, which can fit inside the place that a 4” filter sock goes into and retrofit to tanks and sumps with fixed sock sections.

Can I use a fleece filter for freshwater fish tanks? 

Yes, fresh or saltwater, coldwater or tropical. You could even use an aquarium one over a small pond, but it may use a whole roll in a day, which would be very expensive long term!

What size fish tank are roller filters suitable for?

With Roller filters its not tank size that matters, but water flow. You will need a section in your sump which is physically large enough to house the roller filter, but if you put too much flow through the unit it will block the unit and turn on the roll much faster, making it less cost effective. Typically models are aimed at flow rates of 3000 or 5000lph. Slow the flow down and the rolls will filter better, while also turning less quickly. 

Does a roller filter out the good stuff too?

Fleece filters are indiscriminate with regard to what they capture. Although they can capture fish and coral foods that enter them, the pros outweigh the cons and fewer free=floating particles equals lower nutrients and less nuisance algae. You won’t have to clean then out every day like filter socks either. The Clarisea has a bypass which you can turn manually if you don’t want food to be captured first around.