Aquarium Filters: Hang-On-Back, Canister or Sponge?
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The filter is where most of your tank's beneficial bacteria grow (Habitattitude notes gravel and decor host them too). Here's how the types differ, per Habitattitude and the makers. Product details are from Fluval's and Aqueon's pages and the listings; we haven't tested them.
Three jobs a filter does
- Mechanical: Habitattitude: mesh filters "remove larger particles and keep the water from becoming cloudy."
- Chemical: filters that "remove waste products and elements that can be toxic to fish," usually with activated carbon.
- Biological: "beneficial bacterial to break down toxic fish waste (ammonia, nitrite)." The University of Florida says a new biofilter needs "six to eight weeks" to build up enough bacteria.
How much flow?
Habitattitude: "an effective pump will circulate your entire tank's volume several times each hour." Bettas are the exception: UF says heavy filtration can stress them.
Hang-on-back filters compared
| Filter | Tank size | Flow | Notes |
|---|---|---|---|
| Fluval AC20 | 5-20 gal | 100 GPH | All media included (Fluval) |
| Fluval AC30 | 10-30 gal | 150 GPH | |
| Fluval AC50 | 20-50 gal | 200 GPH | |
| Fluval AC70 | 40-70 gal | 300 GPH | |
| Aqueon QuietFlow 20 | Up to 30 gal (title) | See box | Self-priming; NoDrip cartridge |
| Aqueon QuietFlow 30 | Up to 45 gal (title) | See box | Cartridge-change LED |
| Marineland Penguin 150 | See box | 150 GPH (title) | Rotating Bio-Wheel |
Fluval figures from Fluval's AC Series page; others from the listings.
Fluval AC Series
Four-stage filtration with all media included, and a "CycleGuard" design: Fluval says changing one of the three media inserts at a time keeps bacteria levels stable. Fluval's site lists the AC Series alongside a legacy AquaClear archive.
Fluval AC50 Power Filter
- Hang-on-back filter for 20-50 US gallons (title)
- Media included (listing)
Fluval AC70 Power Filter
- Hang-on-back filter for 40-70 US gallons (title)
- Media included (listing)
Aqueon QuietFlow LED PRO
Aqueon lists 5-stage filtration with a slot for specialty pads (ammonia reducer, carbon or phosphate remover), a self-priming pump that restarts after power cuts, and a NoDrip cartridge holster.
Aqueon QuietFlow 20 LED PRO Power Filter
- For tanks up to 30 gallons (title)
- 5-stage filtration with specialty pad slot, per the listing
- Self-priming internal pump; NoDrip cartridge
Aqueon QuietFlow 30 LED PRO Power Filter
- For tanks up to 45 gallons (title)
- LED flashes when the cartridge needs changing, per the listing
- Self-priming
Marineland Penguin Bio-Wheel
The Bio-Wheel rotates for "wet/dry biological filtration," per the listing.
Marineland Penguin 150 Bio-Wheel Filter
- 150 GPH power filter (title)
- Rotating Bio-Wheel for wet/dry biological filtration, per the listing
- Uses Rite-Size cartridges
Maintenance
Don't replace everything at once. Fluval's BioMax listing says to replace only half the media at a time "to allow proper seeding." More in water changes and maintenance.
FAQ
What size filter?
One that turns the tank over several times an hour.
Three types of filtration?
Mechanical, chemical, biological.
Replace all media at once?
No; change part at a time.