Fluval Pre-Set Aquarium Heater

• Fixed 24–26°C output – no dial means no risk of an accidental temperature change.
• Shatterproof polymer body – safer around active fish and inquisitive hands than glass.
• Fully submersible – the whole unit, cord included, can sit underwater.
• LED running indicator – a light confirms the heater is drawing power.
• Two wattages – 10 W for up to 10 L, 25 W for up to 25 L, so you can match it to the tank rather than oversize it.

Match the heater to your actual tank volume, not the tank you plan to grow into. The 10 W is rated for tanks up to 10 L; the 25 W for tanks up to 25 L. Fluval notes that in a cold room – below about 17°C ambient – even a correctly-sized heater may struggle to hold 24–26°C, and a higher-wattage model is the safer choice.

• Suitable for small freshwater and marine tanks, nano setups, betta bowls and quarantine tubs at the rated volume.
• Not suitable if you need a specific target temperature outside 24–26°C – this heater has no dial, so species needing warmer or cooler water need an adjustable heater instead.
• Not suitable for tanks larger than the rated volume – undersizing a heater means it can run continuously without reaching temperature.

Fully submerge the heater before switching it on, and always unplug it before removing it from the water – running a heater dry can crack the casing. Because the temperature isn't adjustable, there's no dial to set incorrectly, but there's also no way to fine-tune it for a fussier species. A heater guard is recommended in tanks with fish or invertebrates prone to resting against warm surfaces.

A heater draws its full wattage only while actively heating – the thermostat cycles it on and off once the tank reaches 24–26°C, so actual running cost is well below the wattage times 24 hours. The exact duty cycle depends on your room temperature and tank insulation, so we haven't published a specific annual figure here.

Covered by Fluval's manufacturer warranty against defects, in addition to your rights under the Australian Consumer Law. Standard parcel delivery.

What temperature does this heater run at?

A fixed 24–26°C, with no adjustment available on either wattage.

Can I use the 10 W version in a 20 L tank?

No – it's rated to 10 L. Oversizing the tank against the heater means it may never reach the target temperature, especially in a cool room. Use the 25 W version instead.

Does it come with a heater guard?

No guard is included. If you keep fish or invertebrates that rest against surfaces, fit a separate guard.

Is it safe for marine tanks?

Yes, both wattages are rated for freshwater and marine use.