Fluval U4 - Poly/Carbon Cartridge (2)
Pack size
2
Water type
Freshwater + Marine
Fits
Fluval U4
Part no.
BA3812
Replace every
1 months
Media type
Poly floss + activated carbon cartridge
Fluval U4 - Poly/Carbon Cartridge (2)
Fresh poly and carbon media for a Fluval U4 that's started running cloudy or smelling musty. This two-pack of poly/carbon cartridges is the chemical and secondary mechanical stage for the Fluval U4 internal filter – polyester floss to catch the fine particles the foam misses, wrapped around activated carbon to pull colour, odour and dissolved organics out of the water.
Key features
- Genuine Fluval U4 cartridge – direct fit, no trimming or repacking
- Poly floss layer – mechanical polish for water clarity
- Activated carbon core – removes discolouration, odour and dissolved organics
- Two cartridges per pack – one full media change for the U4's cartridge stage
Specifications
| Fits | Fluval U4 internal filter only |
|---|---|
| SKU | BA3812 |
| Type | Poly floss + activated carbon cartridge |
| Pack size | 2 cartridges |
| Water type | Freshwater and marine |
Will it fit my filter?
These cartridges are sized for the Fluval U4 (rated to 240 L / 65 US Gal, 1,000 L/h), which ships with two as standard. They are not interchangeable with the smaller U1, U2 or U3 cartridges – check the model moulded into the filter body first.
Care and maintenance
Activated carbon has a working life, not an indefinite one – once it's saturated it stops adsorbing and can start releasing what it's captured back into the water. Fluval's general guidance is to replace carbon media roughly monthly for consistent clarity; tanks with heavy bioload or tannin-heavy décor will exhaust it faster. Rinse the poly side in removed tank water between changes if it's still catching debris.
Suitable for
Freshwater and marine aquariums running a Fluval U4. Not a biological media – leave the U4's BIOMAX rings in place when you change this cartridge, since that's where the bacteria colony actually lives.
Warranty and delivery
Genuine Fluval part, covered against manufacturing defects, in addition to your rights under the Australian Consumer Law, which cannot be excluded. Ships as a standard parcel.
Common questions
Does this replace all the media in my U4?
No – the U4 also runs foam pads and BIOMAX biological rings, sold separately. This cartridge covers the poly/carbon stage only.
How often should I change it?
Around monthly for most tanks, sooner if the water is heavily stocked or discoloured by driftwood or tannins.
Will running carbon remove my medication?
Yes. Remove carbon media, including this cartridge, before dosing any fish medication, and don't replace it until the course is finished.
