The Best Filter Options for a 5-Gallon Betta Fish Tank Compared

Betta fish need a filter — but not just any filter. The wrong one creates currents that exhaust their long fins, cause chronic stress, and push them into decorations. The right one keeps water clean with gentle, barely perceptible flow.

We compared sponge filters, hang-on-back (HOB) filters, and internal filters in 5-gallon betta tanks to find the best options. Here’s how they stack up.

Quick Comparison

Why Your 5-Gallon Betta Tank Needs a Filter

Every fish produces ammonia through waste and respiration. In a 5-gallon tank, ammonia concentrations spike fast — a single betta can produce toxic ammonia levels within 2-3 days without filtration. Ammonia burns gills, damages fins, suppresses the immune system, and kills at concentrations invisible to the naked eye.

A filter solves this by housing beneficial bacteria that convert ammonia into nitrite, then into nitrate — a far less toxic compound removed by weekly water changes. This process is called the nitrogen cycle, and it’s the foundation of every healthy aquarium.

The Three Types of Aquarium Filtration

Understanding what each filtration type does helps you choose the right filter for your betta.

Biological filtration is the most important. Beneficial bacteria (primarily Nitrosomonas and Nitrobacter) colonize porous filter media — sponges, ceramic rings, bio-balls — and break down ammonia and nitrite. This is the non-negotiable type. Every filter should provide it, and sponge filters excel at it because their entire surface area is colonizable.

Mechanical filtration physically traps debris — uneaten food, plant matter, fish waste particles — as water passes through sponges, pads, or floss. It keeps water visually clear but doesn’t detoxify anything. The trapped debris still decomposes unless you rinse the media regularly.

Chemical filtration uses activated carbon, zeolite, or specialty resins to adsorb dissolved compounds — tannins (yellow water), medications, odors, and some dissolved organics. It’s useful in specific situations but not essential for day-to-day betta care. Carbon exhausts after 3-4 weeks and must be replaced.

The Best Filters for 5-Gallon Betta Tanks

1. AQUANEAT Bio Sponge Filter — Best Overall

The AQUANEAT Bio Sponge Filter is air-driven — it has no motor. An external air pump (sold separately) pushes air through a tube into the base, creating a gentle stream of bubbles that draws water through the two sponge columns. This is the gentlest possible filtration method, and the dual-sponge design means significantly more surface area for beneficial bacteria compared to single-sponge alternatives.

What makes it great for bettas: The water movement is so subtle that even the most long-finned halfmoons and crowntails swim freely around it. There’s no directional output jet — just bubbles rising to the surface, creating light circulation without pushing your betta around. It’s also completely silent, which matters in bedrooms and offices.

What it doesn’t do: It won’t remove tannins, medications, or dissolved chemicals (no chemical filtration stage). Water may develop a slight yellow tint if you use driftwood. This rarely matters for betta health, but if crystal-clear water matters to you, drop a small bag of activated carbon next to it in the tank.

You’ll also need: A small air pump and airline tubing. Add a check valve on the airline to prevent back-siphoning during power outages — they cost under $2 and prevent a flooded floor.

Maintenance: Squeeze the sponges in a bucket of old tank water every 2-4 weeks during water changes. That’s it. Never rinse in tap water — chlorine kills the beneficial bacteria colony you’ve spent weeks building. The sponges last years before needing replacement.

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2. Tetra Whisper IQ Power Filter — Best HOB

The Tetra Whisper IQ is a hang-on-back filter that addresses the two biggest HOB complaints: noise and priming. The submerged motor sits inside the filter body (not above the waterline like most HOBs), which dramatically reduces vibration noise. Tetra’s SoundShield housing adds a second layer of sound dampening. The result is one of the quietest HOB filters available — a genuine advantage over competitors when your tank sits in a bedroom or office.

StayClean technology: The Whisper IQ uses a hinged lid that stays closed during cartridge changes, keeping the bio-grid wet and preserving some beneficial bacteria. This is a meaningful improvement over older HOB designs where removing the cartridge exposes everything to air.

The flow issue for bettas: Like all HOB filters, the Whisper IQ creates a waterfall-style output that can produce more current than long-finned bettas prefer. Manage this by:

Cartridge note: The Whisper IQ uses Tetra’s proprietary Bio-Bag cartridges. When you replace the cartridge, you’re discarding some biological media. Mitigate this by placing a small bag of ceramic bio-rings or an extra sponge inside the filter chamber that stays in place permanently — this preserves your bacteria colony through cartridge changes.

Best for: Plakat (short-fin) bettas, keepers who want crystal-clear water, or community tanks with betta-compatible tank mates that benefit from stronger filtration.

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3. Tetra Whisper 4i Internal Filter — Best for Small Setups

The Tetra Whisper 4i is an internal filter — it mounts inside the tank using suction cups rather than hanging on the rim. It’s significantly smaller than most internal filters, making it a good fit for 5-gallon setups where space matters.

Why it works for bettas: The 4i’s flow rate is inherently low because it’s designed for tanks up to 4 gallons. In a 5-gallon tank, this slight under-rating actually benefits bettas — the output is gentle enough that most bettas swim comfortably around it without baffling. The output is directional, so aim it at the glass wall to further disperse any current.

The capacity trade-off: Being rated for 4 gallons means the filtration capacity is on the edge for a 5-gallon tank with a betta. For a single betta with no tank mates and regular weekly water changes, it handles the bioload fine. If you add shrimp, snails, or live plants that shed debris, supplement with a marimo moss ball or two — they absorb nitrates and provide additional biological surface area.

Maintenance: The cartridge is accessed from the top without removing the filter from the tank. Replace it every 3-4 weeks. Like all cartridge-based filters, keep a separate piece of sponge or ceramic media in the chamber to preserve your bacteria colony through changes.

Best for: Tanks with tight lids or hoods, keepers who want invisible filtration, and setups where a HOB isn’t practical.

How to Choose the Right Filter for Your Betta

Decision Framework

The right filter depends on three factors: your betta’s fin type, your tank size, and how much maintenance you’re willing to do.

Choose the AQUANEAT sponge filter if:

• You have a long-finned betta (halfmoon, crowntail, veiltail)
• You want the simplest, lowest-maintenance option
• You prioritize biological filtration and silent operation
• Your tank is 5-10 gallons with a single betta

Choose the Tetra Whisper IQ (HOB) if:

• You have a short-finned betta (plakat) or a community tank with tank mates
• You want all three filtration types (bio, mechanical, chemical)
• You want crystal-clear water and are willing to baffle the output
• Quiet operation matters (bedroom/office tank)

Choose the Tetra Whisper 4i (internal) if:

• Your tank has a tight lid or hood that won’t accommodate a HOB
• You prefer all equipment hidden inside the tank
• You have a single betta with a light bioload
• You want the most compact, unobtrusive option

Signs Your Filter Is Too Strong

If your betta displays any of these behaviors after installing a filter, the flow is too strong and needs to be reduced or the filter swapped:

Filter Maintenance Schedule

Proper filter maintenance keeps your nitrogen cycle healthy without letting debris accumulate. The key rule: never clean all media at once, and never rinse anything in tap water — chlorine kills beneficial bacteria instantly.

Setting Up a New Filter: The Cycling Process

A brand-new filter has no beneficial bacteria — it’s biologically inert. Before adding your betta, you need to cycle the tank to establish the nitrogen cycle. This takes 2-4 weeks.

Fishless cycling steps: Add a source of ammonia (pure ammonia drops or fish food left to decompose), run the filter 24/7, and test water parameters every 2-3 days. When ammonia and nitrite both read 0 ppm within 24 hours of adding ammonia, the cycle is complete.

Shortcut: Seed your new filter with established media — a used sponge from a running tank, a handful of gravel from an established aquarium, or a bottle of live bacteria (like Fritz TurboStart) can dramatically speed up cycling.

The Bottom Line

For most betta keepers with a 5-gallon tank, the AQUANEAT sponge filter is the best choice. It provides excellent biological filtration with virtually zero current, runs silently, and requires almost no maintenance. It’s the safest option for any betta fin type, and with a 4.7-star rating across thousands of reviews, it’s proven reliable.

If you want the extra polish of mechanical and chemical filtration, the Tetra Whisper IQ is the best HOB option — just plan to baffle the output for any long-finned betta. And if your tank setup doesn’t accommodate external equipment, the Tetra Whisper 4i tucks neatly inside with a naturally gentle flow.

Whatever filter you choose, watch your betta. They’ll tell you if the flow is wrong. A happy betta swims freely throughout the entire tank, explores every level, and comes to the front when you approach. A stressed betta hides, clamps its fins, and avoids the filter side. When in doubt, less flow is always better.