Hang-on-back or internal filter: which to choose for your aquarium?
Published by Planète Pets · managing editor: Clément Lacaille · how our guides are written
For a 20-to-100-litre tank, the hang-on-back (HOB) filter beats the internal filter in most cases: it takes up no room in the tank, is serviced without plunging your hands in the water and oxygenates the surface. The internal filter keeps two trump cards: a rock-bottom price (10 to 25 € versus 20 to 45 €) and total discretion outside the cabinet.
Contents · 5 sections
How do these two filters work?
The internal filter is a submerged unit suction-cupped to a pane: a pump draws water through a sponge. The hang-on-back filter straddles the rim of the tank: water is drawn up through an intake tube, passes through the media in an external box, then falls back as a curtain of water. Both provide the mechanical and biological filtration essential to healthy water.
What are the decisive advantages of the hang-on-back filter?
- Usable volume preserved: nothing in the tank except the intake tube, precious in a nano.
- Clean maintenance: lift the lid, rinse the sponge, no arm-soaking required.
- Modular filter media: sponge, ceramic and floss combine freely.
- Free oxygenation: the falling water stirs the surface, often removing the need for an air pump.
When does the internal filter remain the right choice?
Three cases: a closed hood with no possible cut-out (the HOB needs an accessible rim), a very tight budget, or a shrimp tank where you want gentle intake protected by a sponge. It’s also the filter supplied in most kits, as explained in our comparison all-in-one kit or separate components — it does the job while you wait for better.
What do they cost to buy and run?
Internal filter for 60 litres: 12 to 25 €, replacement sponges 5 to 8 € per year. Equivalent hang-on-back: 25 to 40 €, cartridges 10 to 20 € per year — tip: replace proprietary cartridges with loose sponge and ceramic, half the price. Electricity consumption is identical, 3 to 6 W, roughly 5 to 10 € per year as detailed in our monthly cost of an aquarium.
Frequently asked questions
Is the hang-on-back filter noisy?
A light trickle, soothing to some, annoying in a bedroom: keep the water level high to reduce the drop, or prefer the internal filter near a bed.
Does a hang-on-back filter suit a betta?
Yes, with the flow set to minimum: bettas shy away from strong currents. A sponge on the intake tube softens the flow further.
Can you run both filters at once?
It’s even good practice on a heavily stocked tank: the internal as backup and the hang-on-back as the main filtration, each hosting bacteria.
An accessory from our shop for this use: Hang-on isolation and breeding box for aquariums (€28.90) · the whole shop
This guide is part of Planète Pets’s Fishkeeping universe. Our advice is general in nature: for any health concern, your veterinarian remains the only reference.
