Aquarium Filter Types Explained: Which One Do You Need?

Your aquarium filter is the life-support system of your tank. It processes fish waste, uneaten food, and decaying plant matter before they turn into toxic ammonia and nitrite. Yet walk into any aquarium shop in Singapore and you will find shelves stacked with sponge filters, hang-on-backs, canisters, internal filters, and more, each claiming to be the best. So which one do you actually need? This guide sits inside our broader Freshwater Aquarium Complete Beginner Hub reference.

This guide breaks down every common aquarium filter type, explains how each works, and recommends the best option based on your tank size, livestock, and budget. Whether you are setting up a 20-litre shrimp tank or a 500-litre planted showpiece, the right filter makes all the difference.

How Aquarium Filtration Works

All aquarium filters perform the same fundamental job: circulating water through media that removes waste. This happens through three types of filtration working together:

• Mechanical filtration — Physically trapping solid particles like fish waste, uneaten food, and plant debris. Think of it as a strainer.
• Biological filtration — Beneficial bacteria colonise porous media and convert toxic ammonia into nitrite, then nitrite into relatively harmless nitrate. This is the most critical function of any filter.
• Chemical filtration — Activated carbon, Purigen, or other chemical media adsorb dissolved organic compounds, discolouration, and odours from the water. Optional but useful in specific situations.

Every filter type performs these functions to varying degrees. The differences lie in capacity, flow rate, convenience, and suitability for different tank setups.

Filter Media Types

Before comparing filters, it helps to understand the media that goes inside them:

Sponge Filters

How It Works

A sponge filter is the simplest design: an air pump pushes air through a tube inside a sponge block, creating an uplift that draws water through the sponge. The sponge acts as both mechanical and biological filtration media, with beneficial bacteria colonising its porous surface.

Pros

• Extremely affordable and nearly indestructible
• Gentle flow, perfect for fry, shrimp, and bettas
• Excellent biological filtration relative to cost
• No risk of trapping small fish or shrimp
• Easy to maintain — just squeeze in old tank water
• Provides supplemental aeration

Cons

• Not the most attractive equipment in a display tank
• Limited mechanical filtration — will not polish water crystal clear
• Requires a separate air pump, which can be noisy
• Not practical as the sole filter for heavily stocked or large tanks

Best For

Nano tanks (under 40L), breeding tanks, hospital tanks, shrimp tanks, and as supplemental filtration in larger setups.

Hang-on-Back (HOB) Filters

How It Works

An HOB filter clips onto the back rim of your tank. A motor draws water up through an intake tube, pushes it through a filter cartridge or customisable media basket, then cascades the clean water back into the tank. The waterfall return provides surface agitation and gas exchange.

Pros

• Easy to install and maintain without reaching into the tank
• Good balance of mechanical, biological, and chemical filtration
• Surface agitation improves oxygenation
• Takes up no space inside the tank
• Many models allow custom media instead of proprietary cartridges

Cons

• Visible behind the tank, which some find unattractive
• Flow can be too strong for nano fish and bettas without modification
• Not suitable for rimless tanks without adaptor brackets
• Limited media capacity compared to canisters

Best For

Small to medium tanks (20-120L) with standard rims. Popular brands in Singapore include AquaClear, Seachem Tidal, and Fluval.

Internal Filters

How It Works

An internal filter sits inside the tank, fully submerged. Water is drawn through sponge or media compartments by a small impeller pump. Some models have adjustable flow direction and spray bars.

Pros

• Completely self-contained — no external components except a power cord
• Works with any tank style including rimless
• Quiet operation when fully submerged
• Affordable and widely available

Cons

• Takes up space inside the tank, reducing water volume and aesthetics
• Limited media capacity
• Maintenance requires reaching into the tank
• Not suitable for larger or heavily stocked tanks

Best For

Small tanks (10-60L), quarantine setups, and tanks where an external filter is not practical. Common choices include Eheim Pickup and Dennerle Corner Filter.

Canister Filters

How It Works

A canister filter is a sealed pressurised container that sits below the tank in the cabinet. Water is drawn from the tank through an intake pipe, pushed through multiple media trays inside the canister, and returned via a spray bar or lily pipe. Canister filters move large volumes of water through substantial amounts of media.

Pros

• Largest media capacity of any standard filter type
• Excellent mechanical, biological, and chemical filtration
• Fully customisable media arrangement
• Hidden in the cabinet — only inlet and outlet pipes visible
• Handles high bioloads effectively
• Quiet when properly set up

Cons

• Higher cost compared to other filter types
• More complex to set up and prime
• Maintenance is less convenient — requires disconnecting hoses
• Potential for leaks at hose connections if not maintained
• Overkill for small or lightly stocked tanks

Best For

Medium to large tanks (60L and above), planted aquariums, and any setup where strong, reliable filtration with minimal visual impact is desired. Top brands available in Singapore include Eheim, Fluval, Oase, and ADA.

Sump Filtration

How It Works

A sump is a separate tank, typically housed in the cabinet below the display tank, connected via an overflow and return pump. Water flows from the display tank into the sump by gravity, passes through compartments holding various media (mechanical, biological, chemical), and is pumped back up. Sumps are the standard for marine aquariums and increasingly popular for large freshwater setups.

Pros

• Enormous media capacity and water volume
• All equipment (heaters, reactors, dosing pumps) can be hidden in the sump
• Increased total water volume improves parameter stability
• Easy to customise compartments for specific needs
• Excellent surface skimming through the overflow

Cons

• Requires a drilled tank or hang-on overflow
• Complex setup and plumbing
• Higher cost for equipment and installation
• Risk of flooding if overflow or return pump fails
• Takes up significant cabinet space

Best For

Marine aquariums of all sizes, large freshwater tanks (200L+), and high-end display aquariums. If you are considering a sump-based system, our marine aquarium service includes full sump design and installation.

Fluidised Bed Filters

How It Works

A fluidised bed filter suspends fine media (typically sand or small granules) in an upward water flow, keeping the particles constantly tumbling. This maximises surface area contact between water and beneficial bacteria. The media remains in constant motion, preventing dead spots and channelling.

Pros

• Exceptionally high biological filtration capacity per unit volume
• No clogging or channelling of media
• Compact size relative to filtration performance

Cons

• Provides biological filtration only — no mechanical or chemical
• Must be used alongside another filter type
• Power interruptions can settle the media, causing bacterial die-off
• Less commonly available in local shops

Best For

Supplemental biological filtration in heavily stocked tanks, breeding facilities, and systems where bioload exceeds the capacity of standard filters.

Undergravel Filters (Outdated)

How It Works

An undergravel filter is a perforated plate placed beneath the substrate. Air-driven or powerhead-driven flow pulls water down through the gravel, which acts as biological filter media. The filtered water returns through uplift tubes.

Why They Are Outdated

• Traps debris in the substrate, leading to anaerobic pockets and hydrogen sulphide
• Incompatible with planted tanks — plant roots clog the plate and disrupt flow
• Cannot be used with fine substrates or aquasoil
• Difficult to clean without dismantling the entire tank
• Every other filter type does a better job with fewer drawbacks

We mention undergravel filters only because you may encounter them in older setups or at some local shops. They are not recommended for any new aquarium.

Filter Type Comparison Table

Singapore Recommendations by Tank Size

Based on what is readily available locally and what works well in Singapore’s tropical conditions:

• Nano (under 40L): A quality sponge filter (Qanvee or Aquael Pat Mini) is the simplest option. For a cleaner look, a small HOB like the AquaClear 20 or a nano canister like the Eheim Classic 150 works well.
• Medium (40-120L): A canister filter is the best investment at this size. The Eheim Classic 250, Fluval 107, or Oase BioMaster 250 are all excellent and widely stocked in Singapore. An HOB like the AquaClear 50 is a more budget-friendly alternative.
• Large (120-300L): A canister filter rated for your tank volume is essential. The Eheim Classic 600, Fluval 307, or Oase BioMaster 600 are popular choices. For heavily planted tanks, pairing a canister with inline CO2 diffusion streamlines your setup.
• XL/Marine (300L+): A sump is the gold standard. It provides unmatched filtration capacity and hides all equipment from view. For marine setups, a sump with a protein skimmer is practically mandatory.

Whichever filter you choose, aim for a turnover rate of 4-6 times the tank volume per hour for freshwater (e.g., a 100-litre tank needs a filter rated at 400-600 litres per hour) and 8-10 times for marine.

Frequently Asked Questions

Can I run two filters on one tank?

Absolutely, and it is often a good idea for medium to large tanks. Running two filters provides redundancy — if one fails, the other keeps the bacterial colony alive while you repair or replace the broken unit. A common combination is a canister filter for primary filtration paired with a sponge filter for supplemental biological filtration and aeration.

How often should I clean my aquarium filter?

Rinse mechanical media (sponges and pads) every 2-4 weeks or when flow noticeably decreases. Always rinse in old tank water, never under the tap, to preserve beneficial bacteria. Biological media like ceramic rings should be gently rinsed every 2-3 months. Never replace all media at once — stagger replacements to maintain your bacterial colony.

Do I need chemical filtration?

For most well-maintained freshwater tanks, chemical filtration is optional. Activated carbon is useful for removing medication after treatment, clearing tannin discolouration from driftwood, and polishing water for special occasions. Purigen is excellent for maintaining crystal-clear water in planted tanks. Neither is a substitute for regular water changes.

Which filter is quietest?

Canister filters are generally the quietest option because they sit inside a closed cabinet, away from the living space. Well-maintained Eheim canisters are virtually silent. HOB filters can produce a gentle waterfall sound that some people find pleasant. Sponge filters depend on the air pump; a quality pump like the Eheim air pump or Tetra Whisper is very quiet.

Need help selecting and installing the right filtration system for your aquarium? Gensou provides expert advice, custom aquarium builds, and ongoing maintenance services across Singapore. Contact us and we will recommend the perfect setup for your tank.

Related Reading

• Aquarium Fish Food Types Explained: Flake, Pellet, Frozen and Live
• How Often Should You Clean Your Aquarium Filter?
• How to Choose the Right Aquarium Filter Type
• How to Clean Your Aquarium Filter Without Killing Bacteria
• How to Clean Your Aquarium Filter Without Killing Bacteria