Do undergravel filters still have value?

Undergravel filters are obsolete technology that have serious drawbacks in modern aquariums. They function by passing water through a gravel substrate, where bacteria colonize. This provides good biological filtration; however, it has drawbacks in the barrelling of anaerobic areas, where hydrogen sulfide gas is produced, which is deleterious to fish in these areas with limited oxygen.

Newer filter systems far exceed undergravel filters in the performance department. Sponge filters enable safer biological processing without the potential risks associated with substrate materials. Mechanical cleaners, such as Canister filters, allow for better mechanical cleaning and flow control. These filters maintain a stable oxygen supply and eliminate the risks associated with anaerobic activity. Additionally, they permit the presence of live plants, which would not be possible in an undergravel filter system.

However, undergravel filters might be suitable for certain situations such as breeding fish in bare-bottom tanks. Even then, powerheads should be used instead of air stones to create proper circulation. Daily gravel cleaning is necessary to prevent the buildup of dangerous gases. Most hobbyists find this type of maintenance to be too difficult or demanding to be successful for an extended period.

Changing from undergravel systems improves aquarium health. When upgrading, be sure to retain part of the old substrate for seeding the new biological media. Run both systems temporarily until the transition is complete. Modern filters ultimately provide easier maintenance and greater reliability for thriving aquariums.

Read the full article: Aquarium Filter Types: Your Essential Guide