Best Aquarium Filters 2025: Complete Buyer's Guide
The definitive guide to choosing the right filter for your tank size, budget, and fish. 10 expert-tested recommendations.
Quick Recommendation
10-20 gallons: AquaClear 20 HOB ($35) | 30-55 gallons: Fluval 207 Canister ($160) | 75+ gallons: Fluval FX4 ($280)
Table of Contents
Top 10 Aquarium Filters Compared
| Filter | Type | Tank Size | Price | Best For |
|---|---|---|---|---|
| AquaClear 20 | HOB | 5-20 gal | $35 | Beginners |
| Marineland Penguin 200 | HOB | 20-30 gal | $28 | Budget |
| Fluval 207 | Canister | 30-45 gal | $160 | Best Overall |
| Eheim Classic 250 | Canister | 40-66 gal | $135 | Reliability |
| Penn-Plax Cascade 700 | Canister | 30-65 gal | $80 | Value |
| Fluval FX4 | Canister | 55-250 gal | $280 | Large Tanks |
| Aqueon QuietFlow 30 | HOB | 20-30 gal | $30 | Quiet |
| Hikari Bacto-Surge Foam | Sponge | 10-40 gal | $18 | Shrimp/Fry |
| Hydor Professional 250 | Canister | 40-75 gal | $110 | Mid-Range |
| AquaClear 70 | HOB | 40-70 gal | $65 | HOB Power |
Highlighted rows = our top picks
Understanding Filter Types
1. HOB Filters (Hang-On-Back)
The most popular choice for small to medium tanks. Attaches to the rim of your tank and uses a simple waterfall return.
Best For:
- • 5-55 gallon tanks
- • Beginners
- • Budget-conscious hobbyists
- • Easy maintenance
Avoid If:
- • You have a 75+ gallon tank
- • Noise is a concern (waterfall sound)
- • You want maximum media capacity
- • You prefer hidden equipment
Price Range: $25-80 | Maintenance: Every 2-3 weeks
2. Canister Filters
Sits below your tank in the cabinet. Pulls water through hoses, filters it through multiple media trays, and returns clean water.
Best For:
- • 30+ gallon tanks
- • Planted tanks
- • Messy fish (cichlids, goldfish)
- • Maximum water clarity
Avoid If:
- • You have a nano tank under 20 gallons
- • Your tank sits on a desk (no cabinet)
- • You're intimidated by priming
- • Budget under $100
Price Range: $80-400 | Maintenance: Every 4-8 weeks
3. Sponge Filters
Powered by an air pump. Water is drawn through a sponge that provides mechanical and biological filtration.
Best For:
- • Shrimp tanks
- • Fry/breeding tanks
- • Hospital/quarantine tanks
- • Gentle water flow
Avoid If:
- • You want chemical filtration
- • You have a heavily stocked tank
- • You dislike visible equipment
- • You keep large messy fish
Price Range: $8-30 | Maintenance: Every 2-4 weeks
4. Internal Filters
Submersible filter that sits inside your tank. Common in small tanks and aquarium kits.
Best For:
- • Nano tanks (5-10 gallons)
- • Temporary setups
- • Turtles/amphibians (no suction risk)
- • Quick setup
Avoid If:
- • You want to maximize swim space
- • You have a 20+ gallon tank
- • You want hidden equipment
- • You need high flow rates
Price Range: $15-50 | Maintenance: Every 1-2 weeks
Best Filters by Tank Size
5-10 Gallon Tanks
TOP PICK AquaClear 20
5-20 gallons | 100 GPH | Customizable media
The gold standard for small tanks. AquaClear's patented re-filtration system and customizable media baskets make this the most versatile HOB filter. Includes foam, carbon, and BioMax media.
Hikari Bacto-Surge Foam Filter
Best for shrimp/betta tanks | Ultra-gentle flow
Perfect for nano tanks with delicate inhabitants. Provides excellent biological filtration without strong currents. Requires a separate air pump.
Check Price on Amazon20-30 Gallon Tanks
BEST VALUE Marineland Penguin 200
20-30 gallons | 200 GPH | Bio-Wheel technology
Unbeatable value with Marineland's patented Bio-Wheel for superior biological filtration. Uses easy-to-find Rite-Size cartridges. Quiet operation and reliable performance.
Check Price on AmazonAqueon QuietFlow 30
15-30 gallons | Ultra-quiet | Self-priming
The quietest HOB filter we've tested. Internal pump design eliminates waterfall noise. 5-stage filtration with dense floss and carbon cartridges.
Check Price on Amazon30-55 Gallon Tanks
BEST OVERALL Fluval 207 Canister Filter
30-45 gallons | 206 GPH | Multi-stage filtration
Our top-rated canister filter. Whisper-quiet operation, crystal-clear water quality, and exceptional build quality. Features AquaStop valves for mess-free maintenance and a 3-year warranty.
Penn-Plax Cascade 700
30-65 gallons | Budget canister option
Best budget canister filter. Includes all media (sponges, bio-floss, carbon, ceramic rings). Not as quiet as Fluval, but delivers solid performance at half the price.
Check Price on AmazonAquaClear 70
40-70 gallons | Best HOB for larger tanks
If you prefer HOB filters but have a larger tank, the AquaClear 70 delivers. 300 GPH flow rate and generous media capacity. A cheaper alternative to canisters for 40-50 gallon tanks.
Check Price on Amazon55-75 Gallon Tanks
MOST RELIABLE Eheim Classic 250
40-66 gallons | German engineering | Ultra-quiet
The Toyota Camry of canister filters: bulletproof reliability. Many hobbyists report 10+ years of continuous operation. Simple design, easy maintenance, virtually silent. Best for those who value longevity over features.
Check Price on AmazonHydor Professional 250
40-75 gallons | Mid-range performer
Often overlooked but excellent mid-tier option. Stacked media basket design, easy priming, and quiet operation. Good balance of features and price.
Check Price on Amazon75+ Gallon Tanks
POWERHOUSE Fluval FX4 Canister Filter
55-250 gallons | 700 GPH | Self-priming
The ultimate canister filter for large tanks. Multi-stage filtration with 5.9L media capacity, Smart Pump technology that monitors and optimizes performance, and automatic self-priming. Worth every penny for serious hobbyists.
Pro Tip: For heavily stocked or messy fish tanks (cichlids, goldfish, oscars), consider running TWO smaller canisters instead of one large one. This provides redundancy and makes maintenance easier.
Understanding the 3 Types of Filtration
1. Mechanical Filtration
Removes visible debris: fish waste, uneaten food, plant matter, and particles.
Media used: Sponges, filter pads, filter floss, pre-filter sponges
Maintenance: Rinse in old tank water every 2-4 weeks
2. Biological Filtration
Beneficial bacteria colonize media and convert toxic ammonia → nitrite → nitrate (the nitrogen cycle).
Media used: Ceramic rings, bio-balls, sintered glass, lava rock
Maintenance: NEVER replace unless deteriorating. Gently rinse only if clogged.
Critical: This is the MOST important filtration type. Without it, ammonia will spike and kill your fish. See our nitrogen cycle guide to learn more.
3. Chemical Filtration
Removes dissolved substances, medications, odors, and discoloration from water.
Media used: Activated carbon, Purigen, ammonia removers, phosphate removers
Maintenance: Replace monthly (carbon) or recharge per instructions (Purigen)
Filter Flow Rate Calculator
Your filter should turn over your tank volume 4-6 times per hour.
Formula: Tank Gallons × 4 (or 6 for messy fish) = Minimum GPH needed
Example: 30-gallon tank × 5 = 150 GPH filter recommended
Need help sizing your tank? Use our aquarium volume calculator.
Filter Maintenance Schedule
Weekly
- • Check flow rate (should be strong and steady)
- • Inspect intake tube for clogs
- • Verify impeller is running smoothly (no rattling)
Every 2-4 Weeks
- • Rinse mechanical media (sponges, pads) in old tank water
- • Check water level (for HOB filters)
- • Clean pre-filter sponge if flow decreases
Monthly
- • Replace activated carbon (if using chemical filtration)
- • Clean impeller and impeller housing
- • Inspect hoses/tubing for kinks or cracks (canister filters)
Every 2-3 Months
- • Deep clean filter housing
- • Gently rinse biological media ONLY if heavily clogged
- • Replace worn mechanical media (sponges falling apart)
Common Mistakes to Avoid
- ❌ Replacing biological media (you'll crash your cycle)
- ❌ Rinsing media in tap water (chlorine kills bacteria)
- ❌ Turning off filter during water changes (bacteria need oxygen)
- ❌ Using filter media that clogs too quickly
- ❌ Ignoring reduced flow (sign of clogged media)
For more maintenance tips, see our complete water change guide.
Frequently Asked Questions
What is the best aquarium filter for beginners?
For beginners, HOB (hang-on-back) filters like the AquaClear 20 or Marineland Penguin are ideal. They're affordable ($25-45), easy to set up in minutes, and simple to maintain. For 20-gallon or smaller tanks, these provide excellent filtration without overwhelming complexity.
What size filter do I need for my aquarium?
Your filter should turn over your tank volume 4-6 times per hour. For a 20-gallon tank, you need a filter rated for 80-120 gallons per hour (GPH). Always choose a filter rated for slightly larger than your actual tank size to ensure adequate filtration, especially if you have messy fish like goldfish or cichlids.
Are canister filters worth the money?
Canister filters are worth it for tanks 40+ gallons, planted tanks, or if you keep messy fish. They offer superior filtration capacity, quieter operation, and better water clarity. For smaller tanks under 30 gallons, a quality HOB filter is usually sufficient and more cost-effective. The Fluval 207 ($160) is our top pick for the 30-45 gallon range.
How often should I clean my aquarium filter?
Clean mechanical filter media (sponges, pads) every 2-4 weeks by rinsing in old tank water. Clean the filter housing every 1-2 months. Never replace biological media unless it's falling apart, as this hosts beneficial bacteria. Chemical media (carbon) should be replaced monthly if you use it.
Can I use a sponge filter for a 20 gallon tank?
Yes, but only for lightly stocked tanks with small fish or shrimp. Sponge filters excel in fry tanks, shrimp tanks, and hospital tanks due to gentle flow. For a community 20-gallon tank with typical fish load, a HOB or small canister filter provides better mechanical and chemical filtration.
What's the difference between mechanical, biological, and chemical filtration?
Mechanical filtration removes debris and particles through sponges or pads. Biological filtration uses beneficial bacteria on ceramic rings or bio-balls to convert ammonia → nitrite → nitrate (the nitrogen cycle). Chemical filtration uses activated carbon or resins to remove dissolved substances, odors, and discoloration. All three work together for optimal water quality.
Do I need a filter if I do frequent water changes?
Yes, absolutely. Water changes remove nitrates but don't provide biological filtration. Your filter hosts the beneficial bacteria that convert toxic ammonia and nitrite into less harmful nitrate. Without a filter, ammonia will spike and kill your fish within days. Even heavily planted tanks benefit from gentle filtration.
Can a filter be too strong for an aquarium?
Yes. Small fish like bettas, guppies, and fry can be stressed by excessive current. If your filter creates too much flow, you can: (1) Use a pre-filter sponge to diffuse the output, (2) Aim the output at the glass to reduce current, or (3) Add decorations/plants to create calm zones. A good rule: fish should swim comfortably without being blown around.
What's better: one large filter or two smaller filters?
For tanks 75+ gallons or heavily stocked tanks, two smaller filters often work better than one large filter. Benefits include: redundancy (if one fails, you have backup), easier maintenance (clean one at a time without disrupting all bacteria), better water circulation, and the ability to customize filtration (one mechanical-focused, one biological-focused).
Our Final Recommendations
Remember: The best filter is one that you'll maintain regularly. A $30 HOB filter that gets cleaned every 2 weeks will outperform a $300 canister filter that gets neglected.