Best Hang-on-Back Filters for Small to Medium Aquariums
Hang-on-back filters, commonly known as HOB filters, remain one of the most popular filtration choices for aquariums up to around 200 litres. They are easy to install, simple to maintain and surprisingly effective when chosen wisely. Finding the best hang on back filter aquarium owners can depend on means balancing flow rate, media capacity and noise level. At Gensou Aquascaping at 5 Everton Park, we frequently recommend HOB filters for nano tanks and mid-sized planted setups, and this guide shares our top picks and practical advice.
How Hang-on-Back Filters Work
A HOB filter hangs on the rear rim of the aquarium. An intake tube draws water from the tank into the filter body, where it passes through one or more stages of media before flowing back into the tank via a spillway or return channel. The design is elegantly simple: no hoses to route, no external canister to find space for, and no priming required in most models. The waterfall-style return also provides gentle surface agitation, which aids gas exchange. For planted tanks, this agitation can be both a benefit and a consideration, as excessive surface movement can off-gas injected CO2.
Key Features to Evaluate
When comparing HOB filters, focus on a few critical specifications. Flow rate should turn over the tank volume four to six times per hour for a community aquarium; a 100-litre tank benefits from a filter rated at 400 to 600 litres per hour. Media capacity is equally important, as a larger chamber allows for more biological and mechanical filtration media. Adjustable flow is a valuable feature for planted tanks and shrimp setups where strong currents are undesirable. Finally, noise level matters, particularly in bedrooms or living rooms. Read user reviews for real-world noise feedback, as manufacturer specifications rarely cover this honestly.
Top HOB Filters for Small Tanks
For nano aquariums of 20 to 50 litres, the AquaClear 20 (also sold as Fluval AquaClear) is a long-standing favourite. It features an adjustable flow control and a spacious media basket that accommodates sponge, carbon and bio-media in separate layers. The Seachem Tidal 35 is another excellent choice, offering a self-priming pump, a maintenance alert indicator and a surface skimmer. Both models are available in Singapore for approximately SGD 35 to 55. For even smaller desktop tanks, the Azoo Mignon 60 provides gentle filtration in a compact package suited to tanks under 20 litres.
Top HOB Filters for Medium Tanks
For tanks in the 60 to 200 litre range, the AquaClear 50 and AquaClear 70 offer the same reliable design in larger sizes, with media baskets that rival some small canister filters in capacity. The Seachem Tidal 55 and Tidal 75 scale up beautifully as well, with the added benefit of a blue LED maintenance indicator. Oase BioPlus filters, while less common locally, are well-built German-engineered units with integrated heater compartments. Expect to pay SGD 50 to 100 for quality HOB filters in this size class. Running two smaller HOB units on a medium tank provides redundancy; if one fails, the other maintains biological filtration while you source a replacement.
Media Customisation for Planted Tanks
One of the great advantages of HOB filters is the ability to customise media. Discard the manufacturer’s disposable cartridges, which are designed to generate recurring sales, and replace them with reusable media. A coarse sponge for mechanical filtration, followed by ceramic rings or bio-balls for biological filtration, is a reliable configuration. If you inject CO2, remove any activated carbon, as it can adsorb trace elements that benefit plants. For shrimp tanks, fit a pre-filter sponge over the intake tube to prevent baby shrimp from being drawn into the filter.
Installation and Positioning Tips
Position the HOB filter on the back panel of the tank, ideally centred or at one end to create a gentle circular flow pattern within the aquarium. Ensure the intake tube reaches close to the substrate to pick up detritus effectively, but not so close that it sucks in substrate particles. The water level in the tank should be high enough that the return waterfall is just a gentle ripple rather than a splashing cascade, which reduces noise and CO2 off-gassing. If your tank has a lid, you may need to cut or modify it to accommodate the filter body.
Maintenance Best Practices
Clean the mechanical filter sponge every two to four weeks by rinsing it in a bucket of old tank water, never under the tap, to preserve beneficial bacteria. Biological media should be left undisturbed unless visibly clogged, and even then only rinsed lightly. The impeller and impeller chamber accumulate biofilm and calcium deposits over time; clean these every two to three months with a small brush. Check the intake strainer regularly for debris. A well-maintained HOB filter can run reliably for years with minimal cost beyond electricity.
Final Verdict
For small to medium aquariums, a quality HOB filter offers an unbeatable combination of simplicity, effectiveness and value. The AquaClear and Seachem Tidal lines consistently top our recommendations. Pair them with customised media, keep up with regular maintenance, and they will serve your tank admirably. Drop by Gensou Aquascaping at 5 Everton Park to see these filters in action and get advice on the best model for your specific setup.
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