How does a sponge filter work?

An air pump pushes air into the filter; rising bubbles lift water, which draws tank water through the sponge, per hygger's listing. The sponge traps particles and hosts beneficial bacteria.

Do sponge filters need an air pump?

Yes. The hygger and AQUANEAT sponge filters are air-driven and need a separate air pump and tubing, per their listings.

Why use a sponge filter for a betta?

Gentle flow. A University of Florida fact sheet says bettas prefer calm water and heavy filtration may harm their health and welfare.

Sponge Filters: Gentle Filtration for Bettas, Fry and Shrimp

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Quick answerA sponge filter is a foam block on an air line: bubbles pull water through the sponge, which traps debris and grows beneficial bacteria. It's gentle and simple, which suits bettas, and with no powered intake many hobbyists use them for fry and shrimp. You'll need an air pump, tubing and ideally a check valve. hygger and AQUANEAT both sell them; the Uniclife dual-outlet pump can run two.

Here's how they work and when they make sense. Product details are from the listings; we haven't tested them.

How it works

hygger's listing explains it: the filter is "powered by an air pump that uses the water-lifting effect generated by rising bubbles and drives water flow through filter sponge." The sponge does mechanical filtration and, once colonized, biological filtration. Habitattitude notes biological filters "take days or weeks to develop."

When to use one

Bettas: UF says bettas "prefer calm water" and "heavy filtration may actually be harmful."
Fry and shrimp: there's no powered intake to pull them in (our reasoning).
Quarantine or spare tanks: a sponge can sit in an established tank's filter or water to stay seeded (our suggestion).

Sponge filters

hygger sells sizes rated for 8-20 and 20-55 gallons with a bio-cotton sponge and a ceramic media chamber; AQUANEAT's double sponge filters are recommended for tanks up to 20 gallons and arrive compressed, so soak them first, per the listings.

8-20 gal

hygger Sponge Filter (Small, 8-20 gal)

Air-driven sponge filter, per the listing
Bio-cotton sponge plus ceramic media chamber
Needs a separate air pump; spare sponge included

Check price on Amazon

20-55 gal

hygger Sponge Filter (Medium, 20-55 gal)

Air-driven sponge filter, per the listing
Bio-cotton sponge plus ceramic media chamber
Needs a separate air pump

Check price on Amazon

Double sponge

hygger Double Sponge Filter

Two-sponge air-driven filter with ceramic media balls, per the listing
2 spare sponges included; fine 60 ppi
Needs an air pump; suction cups to mount

Check price on Amazon

4 pack, up to 20 gal

AQUANEAT Double Bio Sponge Filter (4 pack)

Recommended for tanks up to 20 gallons, per the listing
Air-driven; mechanical and biological filtration
Arrives compressed; soak before use

Check price on Amazon

An air pump

The Uniclife pump is listed at 64 GPH max airflow and 4W, with an adjustable knob, two outlets, air stones, tubing and check valves.

Dual outlet, check valves

Uniclife Dual Outlet Air Pump

Max 64 GPH air flow, 4W, per the listing
Adjustable knob; two outlets
Air stones, tubing and check valves included

Check price on Amazon

Cleaning

AQUANEAT's listing says to rinse and squeeze the sponge in tank water. That keeps the bacteria alive; see water changes and maintenance.

Sponge Filters: How They Work and When to Use One

How it works

When to use one