HMF (Hamburg Matten Filter) systems are highly efficient and ideal for multi-tank setups since they can be operated via a central air pump. While blue filter mats are the industry standard, I tested a theory using a cheaper black foam mat.
Materials and Observations
A 50x65x5cm black foam mat was purchased for 40 DKK. Although the dimensions are similar to aquarium-grade mats, standard foam is often harder to clean. The specialized manufacturing process of blue mats ensures an open-cell structure optimized for aquatic use, which justifies their higher price point.
Installation Procedure
The mat must be cut to fit snugly against the aquarium glass. It relies on tension to stay in place, so it must be slightly wider than the internal width of the tank. Using a bread knife or insulation knife along a metal spirit level ensures a clean, straight edge. When measuring, always account for the glass thickness and any frame recesses. For a 50cm wide tank with 10mm glass, I cut the mat to 47.5cm to ensure a secure fit.
The Physics of the Airlift
The system operates on the same principle as an undergravel filter: air pushes water up through a riser pipe, creating a vacuum. This vacuum pulls water through the foam mat, where mechanical debris is trapped and biological filtration occurs. It is important to position the intake of the lift pipe above the substrate level to avoid sucking settled waste back into the main water column.
Conclusion
While this alternative works and saves a small amount of money, I recommend investing in dedicated aquarium filter mats. The superior ease of cleaning and long-term performance of the blue mats make the extra cost worthwhile.
