Important:Quick pick: for most 20 to 40 gallon tanks, a hang-on-back filter rated for your tank size is the easiest and cheapest choice. Prices and links below are demo placeholders.
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Filter types compared
| Type | Best for | Maintenance | Price range |
|---|---|---|---|
| Hang-on-back | 20 to 55 gal tanks | Easy | $20 to $60 |
| Sponge | Fry, shrimp, small tanks | Very easy | $8 to $20 |
| Canister | 55 gal and larger | Moderate | $80 to $250 |
| Internal | 5 to 20 gal tanks | Easy | $12 to $35 |
Hang-on-back filter
Pros
- Cheap and easy to set up
- Simple cartridge changes
- Quiet in most models
Cons
- Can be noisy if water level drops
- Limited media space
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Sponge filter
Pros
- Safe for baby fish and shrimp
- Excellent biological filtration
- Very low cost
Cons
- Needs an air pump
- Little mechanical filtration
See the demo sponge filter deal.
Buying checklist
Before you buy a filter
- Match the flow rate to your tank size
- Pick one with replaceable, rinsable media
- Check noise level in reviews
- Plan a spare part and cartridge budget
FAQ
Frequently asked questions
How big should my filter be?
Aim for a flow rate that turns over the tank volume about 4 times per hour.
Should I replace filter media often?
No. Rinse it in old tank water; replacing everything removes the bacteria that keep fish safe.
