Best Hang-on-Back Filters: Simple Filtration That Works

Table of Contents

• How HOB Filters Work
• Pros of HOB Filters
• Cons of HOB Filters
• Popular HOB Models in Singapore
• Comparison Table
• Customising Your HOB Media
• Sizing by Tank
• HOB vs Canister vs Sponge Decision Guide
• Frequently Asked Questions

How HOB Filters Work

Hang-on-back filters, commonly shortened to HOB filters, are among the simplest and most popular filtration systems in the aquarium hobby. As the name suggests, they hang on the rear rim of your aquarium, drawing water up through an intake tube, passing it through filter media inside a compact box, and returning it to the tank via a waterfall-style spillway.

The basic mechanism is straightforward. A small impeller pump inside the filter body pulls water from the tank through the intake tube. Water then flows through one or more compartments containing mechanical, chemical and biological media. Gravity returns the filtered water to the tank, creating surface agitation that aids gas exchange. This self-contained design means there are no external hoses, no separate pump to install and no plumbing to worry about.

For hobbyists in Singapore running nano tanks or mid-sized setups on HDB shelving units, HOB filters offer a neat, space-efficient solution. They sit entirely behind the tank, leaving the sides and front uncluttered.

Pros of HOB Filters

• Easy installation — Clip on the back of the tank, fill with water, plug in. Most hobbyists can set one up in under five minutes without any tools.
• No hose plumbing — Unlike canister filters, there are no inlet and outlet hoses to route, secure or worry about leaking.
• Visible media — You can lift the lid and inspect or swap media without disconnecting anything. This makes maintenance fast and intuitive.
• Affordable — Entry-level HOB filters start from around SGD 15-25, making them accessible for beginners.
• Good surface agitation — The waterfall return creates excellent gas exchange, which helps oxygenate the water in Singapore’s warm 28-32°C conditions where dissolved oxygen is naturally lower.
• Self-priming — Most modern HOB filters prime themselves after a power outage, unlike some canister filters that may need manual re-priming.

Cons of HOB Filters

• Waterfall noise — The cascading return can be noisy, especially if the water level drops slightly. In small HDB bedrooms, this can be disruptive at night.
• Limited media capacity — Compared to canister filters, HOB units hold significantly less media, which limits their biological filtration capacity for heavily stocked tanks.
• Evaporation — Singapore’s warm ambient temperatures (often 28-32°C indoors without air conditioning) accelerate evaporation. As the water level drops, the waterfall distance increases, creating more splash and noise. You may need to top up every few days.
• Aesthetic limitations — The filter box is visible from the back and sometimes from the sides, which can detract from open-top aquascapes.
• Not ideal for planted tanks — Strong surface agitation from the waterfall can off-gas CO2, which is counterproductive if you are injecting CO2 for a planted aquascape.

Popular HOB Models in Singapore

AquaClear Series (by Fluval)

The AquaClear range is arguably the gold standard for HOB filters. Available in five sizes (AquaClear 20, 30, 50, 70 and 110), they use a modular media basket system rather than proprietary cartridges. This means you can fill the basket with whatever media you prefer — foam, bio rings, activated carbon or any combination. The adjustable flow control is a genuine bonus for betta tanks or shrimp setups where gentle flow is important.

Seachem Tidal Series

Seachem’s Tidal filters (35, 55, 75 and 110) are a newer entrant that has gained a loyal following. They feature a self-priming pump, a surface skimmer attachment, and a maintenance alert that indicates when flow has dropped. The media basket pulls out from the top, making cleaning simple. The Tidal also has a heater slot, which is a thoughtful touch for smaller tanks.

Fluval C Series

The Fluval C series (C2, C3, C4) uses a multi-stage filtration system with separate mechanical, chemical and biological compartments. Each stage has its own tray, so you can service one stage at a time without disrupting the others. They are well-built but tend to be pricier than AquaClear equivalents.

Budget Options

For hobbyists on a tighter budget, brands like SunSun, Dophin and ISTA offer HOB filters from SGD 15-30. These are perfectly adequate for small to mid-sized tanks. They typically use cartridge-based media, but you can often bypass the cartridge and pack in your own media with a little creativity.

Comparison Table

Customising Your HOB Media

One of the biggest mistakes beginners make is relying solely on the cartridge that comes with their HOB filter. Most stock cartridges are thin pads with a layer of activated carbon — designed to be replaced entirely every few weeks. This is problematic because replacing the entire cartridge also removes your established beneficial bacteria.

Step 1: Remove the Carbon Cartridge

Unless you are actively removing medication or tannins, activated carbon is unnecessary for most setups. Remove the stock cartridge and replace it with a cut-to-fit sponge for mechanical filtration.

Step 2: Add Biological Media

Fill any remaining space with ceramic rings, bio balls or Seachem Matrix. These porous materials provide enormous surface area for nitrifying bacteria. In Singapore’s warm water, bacterial colonies establish quickly but also consume more oxygen, so maximising bio media is beneficial.

Step 3: Layer Properly

Water should flow through mechanical filtration (sponge or floss) first, then through biological media. This prevents debris from clogging your bio media. Some hobbyists add a thin layer of Purigen or activated carbon at the very end for water polishing.

If you are unsure which media combination to use, our guide on aquarium filter types explained covers media choices for every filter style.

Sizing by Tank

A common rule of thumb is to choose a HOB filter rated for at least 1.5 to 2 times your actual tank volume. This accounts for the fact that manufacturer ratings are often optimistic and that media customisation can slightly reduce flow.

HOB vs Canister vs Sponge Decision Guide

Choosing between a HOB, canister and sponge filter depends on your priorities.

For planted aquascapes, canister filters are generally the better choice. But for a simple community tank, a well-customised HOB filter is hard to beat for the price. Many experienced hobbyists in Singapore keep a HOB filter on their quarantine tank and a canister on their display tank — the best of both worlds.

Frequently Asked Questions

Can I use a HOB filter on a rimless tank?

Yes, but check the clip width. Most HOB filters are designed for standard-thickness glass (6-10mm). Rimless tanks with thicker glass (10-12mm) may require you to adjust or modify the mounting bracket. Some models, like the Seachem Tidal, have adjustable levelling systems that accommodate different glass thicknesses.

How often should I clean my HOB filter?

Rinse the mechanical filtration sponge in old tank water every two to four weeks. Never rinse biological media under tap water — PUB-treated water contains chloramine, which kills beneficial bacteria instantly. Replace the sponge only when it starts to fall apart. Bio media can last years without replacement.

Will a HOB filter work during a power outage?

No. HOB filters rely on an electric impeller pump. During a power outage, all filtration and water circulation stops. We recommend keeping a battery air pump on hand for emergencies — power outages in Singapore are rare but can be devastating when they occur.

Is a HOB filter good for a planted aquarium?

HOB filters work for low-tech planted tanks without CO2 injection. However, the waterfall return creates significant surface agitation that off-gasses dissolved CO2. If you are running a high-tech planted aquascape with pressurised CO2, a canister filter with a submerged outlet (such as a lily pipe or spray bar) is a better choice.

Whether you are setting up your first community tank or outfitting a quarantine setup, the right HOB filter makes fishkeeping simpler. If you need help choosing a filter for your specific setup, visit us at 5 Everton Park — our team has over 20 years of experience matching equipment to aquariums of every size.

Related Reading

• Best Hang-on-Back Filters for Small to Medium Aquariums
• Best Hang-On Filters for Nano Planted Tanks
• Best Hang-On-Back Refugiums for Aquariums
• Best Biological Filter Media for Aquariums: Ceramic, Sintered and Bio Balls
• Best Hang-On Breeding Boxes for Aquarium Fry Isolation