Aquatics
Aquarium Filters
The filter is the life support system of an aquarium. Its real job is to host the bacteria that convert ammonia to nitrite and nitrite to nitrate, not simply to trap debris.
What matters
- Biological media volume
- The single most important figure — more media surface means a more stable cycle.
- Turnover rate
- Roughly four to six times the tank volume per hour for community tanks, lower for bettas.
- Flow adjustability
- Essential for long-finned fish, axolotls and shrimp.
- Maintenance access
- You will open it monthly; awkward designs get neglected.
- Noise
- Matters more than buyers expect in a bedroom or living room.
Types and options
Sponge filter with air pump
Best for: Shrimp, fry, bettas, quarantine and hospital tanks
Watch out: Limited mechanical filtration; air pumps hum
Hang-on-back filter
Best for: Tanks up to around 150 litres
Watch out: Cartridge-based models throw away your bacteria every month — use reusable media instead
Canister filter
Best for: Larger or heavily stocked tanks
Watch out: More expensive and needs careful leak checks at seals
Internal power filter
Best for: Small tanks with limited space behind
Watch out: Takes up in-tank swimming space
Buying notes
Never clean filter media in tap water — chlorine kills the bacterial colony. Rinse it gently in a bucket of the tank water you just removed during a water change.