Best Aquarium Filters: Complete Buyer's Guide

Your filter is the most critical piece of equipment in your aquarium. It is responsible for mechanical filtration (removing particles), biological filtration (housing the beneficial bacteria that process waste), and sometimes chemical filtration (removing dissolved impurities). Choosing the right filter will make the difference between a healthy, low-maintenance tank and a constant battle with water quality.

Types of Aquarium Filters

Hang-On-Back (HOB) Filters

Best for: Beginners, small to medium tanks (20-200 liters)

HOB filters hang on the rim of your tank and draw water up through a tube, pass it through filter media, and return it as a gentle waterfall. They are affordable, easy to maintain, and provide good surface agitation for gas exchange.

Top picks:

• Fluval AquaClear series — Customizable media baskets, adjustable flow rate, excellent biological filtration capacity
• Seachem Tidal series — Self-priming, surface skimmer included, large media capacity

Pros: Easy to set up and maintain, affordable, good for planted tanks with adjustable flow Cons: Visible on the back of the tank, can be noisy if water level drops, limited media capacity compared to canisters

Canister Filters

Best for: Medium to large tanks (60+ liters), planted tanks, aquascapes

Canister filters sit below or beside the tank and connect via intake and output hoses. They offer the largest media capacity, the most customizable filtration, and are nearly silent in operation.

Top picks:

• Oase BioMaster Thermo — Built-in heater, pre-filter system, excellent build quality
• Eheim Classic series — Legendary reliability, German engineering, virtually indestructible
• Fluval 07 series — Great value, easy maintenance, quiet operation

Pros: Large media capacity, highly customizable, very quiet, keep equipment out of the tank Cons: More expensive, slightly more complex setup, need to be careful about leaks

Sponge Filters

Best for: Breeding tanks, shrimp tanks, hospital tanks, nano tanks

Sponge filters are powered by an air pump and provide gentle mechanical and biological filtration. They are incredibly simple, cheap, and safe for fry and shrimp that might get sucked into other filter types.

Top picks:

• Aquarium Co-Op coarse sponge filter — Excellent biological filtration surface area
• Hikari Bacto-Surge — Available in multiple sizes, reliable design

Pros: Shrimp and fry safe, very cheap, excellent biological filtration, no moving parts to break Cons: Not the most attractive, limited mechanical filtration, requires a separate air pump

Internal Filters

Best for: Small tanks, nano setups, as supplementary filtration

Internal filters sit inside the tank, taking up some space but offering quiet operation and easy maintenance.

Top picks:

• Dennerle Scaper's Flow — Designed for planted nano tanks, very quiet, adjustable flow
• Fluval U series — Versatile, submersible, three-stage filtration

How to Choose the Right Filter

Consider these factors when making your decision:

1. Tank size: Your filter should be rated for at least your tank volume; ideally 4-10x turnover per hour
2. Livestock: Shrimp and fry need gentle filtration; large messy fish need powerful filtration
3. Planting level: Heavily planted tanks benefit from the customization of canister filters
4. Budget: Sponge filters start under $10; premium canisters can exceed $200
5. Noise tolerance: Canisters are the quietest; HOBs can splash; sponge filters bubble
6. Aesthetics: If you want nothing visible inside the tank, a canister filter is your best bet

Filter Media: What Goes Inside

Regardless of filter type, the order of media matters:

1. Mechanical (first): Coarse sponge or filter floss to trap debris
2. Biological (middle): Ceramic rings, bio-balls, or sintered glass — this is where beneficial bacteria live
3. Chemical (optional, last): Activated carbon, Purigen, or phosphate removers for polishing

Pro tip: Never replace all your media at once. Stagger replacements to preserve your bacterial colony.

Maintenance Tips

• Clean mechanical media weekly or bi-weekly by rinsing in old tank water
• Never clean biological media in tap water (chlorine kills bacteria)
• Replace chemical media according to manufacturer guidelines (usually monthly)
• Check impellers quarterly for debris buildup
• For canister filters, keep spare O-rings and lubricant on hand

Our Recommendation

For most aquarists setting up a planted community tank in the 60-120 liter range, a canister filter offers the best combination of performance, silence, and flexibility. The Oase BioMaster Thermo is our top pick thanks to its integrated heater, and the Fluval 207 is an excellent budget-friendly alternative.

For nano tanks and shrimp setups, you cannot beat a simple sponge filter paired with a quality air pump.