Choosing a filter: HOB vs canister vs sponge

Short answer: for most beginners a hang-on-back (HOB) filter is the easiest all-rounder and a great choice for community tanks from about 10 to 55 gallons. A sponge filter is cheap, gentle and ideal for nano tanks, shrimp, fry and quarantine. A canister filter holds the most media and hides in the cabinet, which makes it the pick for larger or heavily stocked tanks, roughly 40 gallons and up. Match the filter to your tank size and to how heavily you plan to stock it.

All three do the same core job: they pass water through media that trap debris and house the bacteria that keep your fish safe. They differ in capacity, gentleness, cost and upkeep.

Hang-on-back (HOB) filters

An HOB hangs on the back rim, lifts water up an intake tube, runs it through media and returns it to the tank. It is the default choice for good reason.

• Best for: most community tanks from about 10 to 55 gallons.
• Strengths: easy to install, easy to reach for maintenance, holds all three media types, and quiet enough.
• Watch for: the intake can be strong for tiny fish or shrimp, though a sponge guard fixes that.

A long-running example is the AquaClear Power Filter, which comes in sizes to match tanks from nano up to large.

Sponge filters

A sponge filter is driven by an air pump. Rising bubbles pull water through a foam block that becomes home to beneficial bacteria. Simple, and quietly excellent at what it does.

• Best for: nano tanks, shrimp tanks, breeding and fry, quarantine and hospital tanks, and bettas.
• Strengths: very gentle flow, no intake to trap small fish, inexpensive, and superb biological filtration.
• Watch for: no chemical filtration, it is visible in the tank, and it needs a separate air pump.

Our Aquatop internal sponge filter comes in several sizes for different tanks.

Canister filters

A canister sits in the cabinet below the tank, with hoses carrying water down to a sealed container packed with media and back up again. It holds far more media than an HOB.

• Best for: larger or heavily stocked tanks, roughly 40 gallons and up.
• Strengths: large media capacity, strong and adjustable flow, hidden from view, and quiet.
• Watch for: higher cost, and a little more effort to open and service. It is often more filter than a small tank needs.

Canister models and sizes change with what is in stock, so ask us for the current options that suit your tank. Matching the filter to the tank properly matters more than the brand on the box.

How to pick, and sizing the filter

Aim for a filter rated for your tank size or the next size up, and target roughly four to six times the tank's volume in flow per hour. A lightly stocked, planted 20 gallon is happy on an HOB; a busy 40 gallon of active fish benefits from a canister; a 5 gallon shrimp tank wants a sponge. When in doubt, a slightly larger filter is rarely a mistake.

Media: the part that actually matters

Whatever the filter, the media inside does the work. There are three kinds:

• Mechanical (foam and floss) traps debris — for example replacement filter foam.
• Biological (ceramic or sintered media) houses your bacteria and should be disturbed as little as possible.
• Chemical (such as activated carbon) is optional and used as needed; a media bag keeps loose media tidy.

You can browse filter media in the external media collection and hang-on-back options in the AquaClear collection. Never replace all of your biological media at once — rinse it gently in old tank water and reuse it, or you will lose the bacteria you worked to grow.

Not sure where a filter fits in the bigger picture? See your first aquarium for the full setup, and size the rest of your gear with our heater sizing guide.

Written by the team at Tropical Fish Imports in Lethbridge, Alberta. Last reviewed August 2026.

Still weighing the options for your exact tank? Bring us the tank size and your stocking plan and we will point you to the right filter — message us or drop by the shop in Lethbridge.