Fluval U1 Foam Insert
Pack size
Single
Water type
Freshwater + Marine
Fits
Fluval U1
Part no.
PF131a
Media type
Mechanical foam pad
Fluval U1 Foam Insert
Genuine replacement foam that keeps a Fluval U1 filtering properly. This is the mechanical media for the U1 internal filter – the foam pad that traps floating debris before it reaches the biological stage, while hosting the bacteria colony that actually keeps the water safe. A clogged, collapsed or worn-out foam pad is the most common reason a U1 loses flow.
Key features
- Genuine Fluval part – sized and shaped for a direct fit, no trimming
- Mechanical filtration – catches suspended debris before it can cloud the tank
- Biological surface – the same foam hosts nitrifying bacteria, so it isn't just a debris trap
- Single insert – sold as one foam pad, matched to the U1's single-foam-stage design
Specifications
| Fits | Fluval U1 internal filter only |
|---|---|
| Part number | PF131a |
| Type | Mechanical foam pad |
| Pack | Single insert |
| Water type | Freshwater and marine |
Will it fit my filter?
This foam is cut for the Fluval U1 only, the smallest filter in the U series (rated to 55 L / 15 US Gal). It is not interchangeable with the U2, U3 or U4 foam pads, which are larger. Check the model number moulded into the filter body before ordering.
Care and maintenance
Rinse the foam in removed tank water at each service rather than tap water, which can kill off the bacteria living in it. Replace it in rotation with the filter's other media rather than all at once, so the colony never has to rebuild from zero. Fluval's own guidance is to replace the foam pad every 3–6 months of normal use – sooner if it stays compacted after a rinse or flow doesn't recover.
Suitable for
Any Fluval U1 running freshwater or marine. Not suitable for the U2, U3 or U4 – order the matching foam for those models instead.
Warranty and delivery
Genuine Fluval part, covered by the manufacturer against defects, in addition to your rights under the Australian Consumer Law, which cannot be excluded. Ships as a standard parcel.
Common questions
Will this fit my U2, U3 or U4?
No. Each filter in the U series takes its own foam pad, sized to that model. This one is sized for the U1 only.
How do I know if it needs replacing rather than just rinsing?
If the foam stays flattened or falls apart after a rinse in tank water, or flow through the filter stays weak after cleaning, replace it.
Should I replace all the media at once?
No – stagger it. Replacing every media type in one visit can crash the bacteria colony and cause a mini-cycle.
