Filters · Hang-on-back
Fluval AC20
Manufacturer-rated for 5–20 US gal aquariums.
Four-stage hang-on-back filter with adjustable flow, a reusable media basket, and maker-rated maximum flow.
Consider: The media basket lifts upward. Leave unobstructed space above the filter so routine cleaning does not require moving the tank.
US version, item 19595. Check what’s in the box before you buy.
Tank size Fluval rates it for
5 to 20 US gal
Choose your tank to see where it falls.
Check it against your tank →Specifications that affect fit
- Manufacturer capacity
- 5–20 US gal
- Power
- 7 W
- Supply voltage
- 120 V / 60 Hz
- Dimensions
- 5.1 × 4.4 × 6.4 in (L × W × H)
- Pump output
- Not published
- Filter circulation
- Not published
- Maximum flow
- 100 GPH
To see what it costs to run, enter the watts on its label and your daily hours in the electricity cost calculator.
Pump output, filter circulation and maximum flow are measured in different ways. Your filter will move less water than the box says once media and hoses are in. Measure it with the flow calculator.
Choosing between sizes
This model’s range is 5–20 US gal; Fluval AC50 is 20–50 US gal. Maximum flow differs: 100 versus 200 GPH. Choose by your tank size and the space you have, not by the family name.
AC50: details and fit →Before choosing this model
- Confirm item 19595 and the AC20 size.
- Measure rear and overhead clearance before buying.
- The manual lists a maximum aquarium rim thickness of 0.9 inches / 2.4 cm. Measure your tank rim before buying.
Our buying guides size it for these tanks:
5 gallon10 gallon20 gallonBetta tankShrimp tank
A filter rated for your tank can still be too tall for your cabinet or too strong for small fish: see how to choose one.
Check it against your tank → Something not working? See the troubleshooting guide.
Choose and care for mechanical, biological and chemical media before buying replacement supplies.
Included items & upkeep
- Bio-Foam
- carbon
- BIOMAX
- intake sponge
Plan for the routine work
- Unplug before service.
- Follow the AC manual for media order, basket service, and impeller cleaning.
To budget for replacement media and supplies, use the first-year cost calculator. For how often and how to clean it, follow the maker’s manual.