How to Choose an Aquarium Filter
Filtration is the heart of a healthy tank.
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Size it to your tank
Aim for a filter rated to turn over your tank volume about 4 times per hour. A 30-gallon tank wants roughly 120 GPH. When in doubt, slightly over-filter — it's hard to have too much.
Filter types
Hang-on-back filters are cheap and easy for most tanks. Canister filters handle larger or planted tanks with more media. Sponge filters are gentle and perfect for shrimp, fry, and bettas.
Biological media matters most
The beneficial bacteria living in your filter media do the real work. Never replace all your media at once or rinse it in tap water — you'll wipe out the colony and re-trigger cycling.
Recommended gear
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FAQ
What size filter do I need?
Roughly 4× your tank volume in GPH — about 120 GPH for a 30-gallon tank. Over-filtering is fine; under-filtering causes waste buildup.