Understanding Aquarium Filtration
Mechanical, biological, and chemical filtration explained. Discover which filter types suit your setup and how to maintain them properly.
Mechanical Filtration
Mechanical filtration physically removes debris, uneaten food, and fish waste from the water column. Filter sponges, floss, and pads trap particles as water passes through them. Coarse media catches large debris first, while fine media polishes the water. Regular rinsing in old tank water keeps mechanical media effective without destroying beneficial bacteria.
Biological Filtration
Biological filtration is the most critical part of any aquarium filter. Beneficial bacteria colonise porous media like ceramic rings, bio-balls, and sponges, converting toxic ammonia into nitrite and then into much less harmful nitrate. This nitrogen cycle is what keeps your fish alive. Never replace all biological media at once, and always rinse it in dechlorinated water.
Chemical Filtration
Chemical filtration uses activated carbon, zeolite, or specialised resins to remove dissolved organic compounds, discolouration, odours, and medication residues from the water. Activated carbon is the most common and works well for general use. It needs replacing every three to four weeks as it becomes saturated and loses effectiveness.
Filter Types Compared
Sponge filters are excellent for shrimp tanks and breeding setups due to their gentle flow. Hang-on-back filters offer good all-round performance and are easy to maintain. Internal filters work well in smaller aquariums. Canister filters provide the best filtration capacity for larger tanks and allow you to customise media layers for your specific needs.
Maintenance Tips
Clean your filter on a regular schedule, roughly every two to four weeks, but never on the same day as a water change. Squeeze sponges in a bucket of old tank water to preserve bacteria colonies. Replace mechanical media when it starts to fall apart, but stagger replacements so you always have established media in the filter. A well-maintained filter is the foundation of a healthy aquarium.
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