The Aqua One AquaReef S2 300 takes the Aqua One Sponge 420s (25420S) for AquaReef S2 300 and AquaReef S2 400 as its filter media; Australian sellers list it from A$29.88 as of 29 October 2026. Fitment confirmed against the manufacturer's compatibility list.
Your aquarium filter
Aqua One AquaReef S2 300
Aquarium filter
Confirmed against Aqua One's listConfirmed against Aqua One's own compatibility list
Not yours? Change
Takes the 25420S filter media
Sponge 420s (25420S) for AquaReef S2 300 and AquaReef S2 400 · check the code printed on your old filter before ordering.
Your aquarium filter
Aquarium filter
Confirmed against Aqua One's listConfirmed against Aqua One's own compatibility list
Takes the 25420S
Filter media · check the code on your old filter.
Other Aqua One aquarium filters that take the 25420S
GenuineGenuine Aqua One
$29.88
Aquarium Spare Parts · 29 OctLowest genuine · Aquarium Spare Parts · checked 29 Oct
CompatibleCompatible option
See seller
No compatible seller tracked yetNo compatible seller tracked yet
Genuine: made by Aqua One. Compatible: another brand.Genuine is made by Aqua One. Compatible is made by another brand. Check the seller's page for the size and models it fits.
Lowest price · $29.88
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AUD, before delivery. Each price shows when it was checked.
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How long it lasts
Replace it when it clogs, breaks down or no longer holds its shape, Aqua One says; until then rinse it in a bucket of aquarium water each time you clean the filter.
How to change the filter media in your Aqua One AquaReef S2 300
Watch the guide or follow the steps.
No clear video for this part yet. The steps cover it.
- 1Turn off the return pump and heaters before you work in the sump.
- 2Take the sponge out of the sump's filter section.
- 3Rinse the sponge in water you have taken out of the aquarium during the water change, never in tap water.
- 4Put the sponge back, or fit a new one once the old one blocks up or breaks down.
- 5Turn the pump and heaters back on and check that the water level is above the minimum operating mark.
Every number this part goes by
- Retail name:
- 25420S
- Retail name:
- 420S
Sellers list any of these; they are the same part.
About your Aqua One AquaReef S2 300
Aqua One aquarium filter — AquaReef S2 aquarium (discontinued). Its filter media is the Sponge 420s (25420S) for AquaReef S2 300 and AquaReef S2 400, part 25420S.
Where the model number is: The model is on the filter's lid, motor head or a label on its side (Fluval 307, Eheim Classic 2215). For a tank with a built-in filter, use the tank's name.
Fits these 2 Aqua One models
Aqua One2 models
Common questions
- Which filter media fits the Aqua One AquaReef S2 300?
- The Aqua One AquaReef S2 300 takes the Aqua One Sponge 420s (25420S) for AquaReef S2 300 and AquaReef S2 400.
- Where can I buy the 25420S in Australia?
- We track 1 Australian seller for the 25420S; the lowest listed price when we last checked was A$29.88 at Aquarium Spare Parts. Prices are re-checked daily and dated on this page.
- How do I fit the 25420S in an Aqua One AquaReef S2 300?
- No tools, a few minutes: 5 steps, listed on this page with the replacement video where the maker has one.
- What happens if I don't change it?
- Spent carbon stops removing odours and discolouration, and clogged pads slow the flow, so the filter moves less water through the tank.
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