OASE FiltoSmart Thermo 300 – External Canister Filter with Heater (up to 300L)

The OASE FiltoSmart Thermo 300 is an external canister filter with a fully integrated 300W heater, built for aquariums up to 300 litres. Instead of running a separate heater and filter — two power cords, two footprints — it combines both jobs into one compact unit that sits quietly next to or behind the tank. Water is drawn out, filtered through three stages, brought to temperature, and returned clean and warm, with nothing visible inside the aquarium but the intake and spray bar.

It's the flagship of OASE's FiltoSmart Thermo line, sized for the upper end of medium-to-large planted, community, and marine setups — the point where a FiltoSmart Thermo 200 starts to feel undersized but a full BioMaster canister feels like more than you need.

What Makes It Different

Most external filters treat the heater as an afterthought — you still buy one separately, still find somewhere to suction-cup it inside the tank, still see the cord. OASE built this filter around the opposite idea: the heater lives inside the canister, in the outflow path, so warmed water is distributed evenly through the return flow rather than sitting as a hot spot in one corner. The result is a tidier tank and one less piece of equipment competing for space behind the glass.

The second thing that sets it apart is how little friction there is in maintenance. EasyClick opening and self-priming startup mean cleaning the media doesn't turn into an afternoon project, and the locking inlet/outlet unit keeps the mess in the bucket instead of on your floor.

Key Benefits

• All-in-one filtration and heating — no separate in-tank heater, no extra cord, no extra suction cups
• Even heat distribution — temperature is regulated in the outflow, not localized around a single heating element
• Full 3-stage filtration — mechanical, biological, and chemical (activated carbon) media in sequence
• Strong flow for the tank size — up to 1000 l/h, adjustable at both inlet and outlet
• Low running cost — the filter pump itself draws just 23W
• Fast, mess-free maintenance — EasyClick opening and a locking inlet/outlet unit for clean disconnects
• Self-priming — no manual suction needed to start water flow after maintenance
• Quiet, sound-dampened operation — suited to living rooms and bedrooms, not just utility spaces
• Carrying handle — makes moving a full canister to the sink far less awkward
• Freshwater and marine compatible
• 3-year manufacturer warranty

Technical Specifications

• Max. aquarium volume: 300 L
• Max. flow rate: 1000 l/h
• Filter power consumption: 23 W
• Integrated heater power: 300 W
• Filter volume: 6.4 L
• Pre-filter volume: 1.5 L
• Hose connection: 16/22 mm
• Dimensions (L x W x H): 462 x 290 x 246 mm
• Filter media included: 20 ppi foam, 10 ppi foam (x2), ceramic biological media, activated carbon foam
• Water compatibility: freshwater and marine
• Warranty: 3 years

What's in the Box

Canister filter with integrated heater, 20 ppi filter foam, two 10 ppi filter foams, ceramic biological media, activated carbon filter media, intake tube with inlet strainer, water distributor nozzle, spray bar, inlet and outlet adapters with flow control, connecting tubing and fittings, removable base, and power cables.

Who Should Use This

The FiltoSmart Thermo 300 suits aquarists running a tank in the 200–300 litre range who want heating and filtration handled by one reliable unit instead of two: planted tanks where every extra cord breaks the composition, tropical community setups that need stable, evenly distributed warmth, and marine tanks where fresh/salt water compatibility genuinely matters. If you're currently running a separate canister filter and in-tank heater on a tank this size, this is a straightforward consolidation — one less appliance, one less thing to maintain.

Setup and Use

1. Position the canister below the waterline, ideally in the cabinet, and connect the intake tube with strainer and the spray bar or distributor nozzle using the supplied tubing and adapters.
2. Fill the canister with water before first startup to assist self-priming, then open the flow control valves gradually.
3. Load the media in sequence — mechanical foams first, then ceramic biological media, then activated carbon — and close the lid using the EasyClick mechanism.
4. Set your target temperature once water is circulating and allow 24 hours to stabilize before fine-tuning.
5. For maintenance, use the locking inlet/outlet unit to disconnect without draining the hoses, carry it to a sink using the handle, and rinse mechanical media in removed aquarium water to protect the bacteria colony.

Expert Tip

Don't rinse all your filter media at once. On a maintenance visit, clean only the mechanical foam stages (the ones that trap visible debris) and leave the ceramic biological media untouched unless it's genuinely clogged. The biological stage is where your nitrifying bacteria colony lives — over-cleaning it on every visit is one of the most common ways aquarists accidentally trigger a mini-cycle and see an ammonia or nitrite spike days later.

Frequently Asked Questions

Can I use it without the heater running?

Yes. The heater and filtration functions operate independently, so you can run it purely as a canister filter if your tank already has adequate heating.

Is this filter suitable for a marine or reef tank?

Yes, OASE lists it as compatible with both freshwater and marine environments. For reef tanks with heavy bioload, it's often run alongside dedicated reef equipment rather than as sole filtration.

How often does the filter media need cleaning?

Mechanical foam typically needs rinsing every 2–4 weeks depending on bioload. Ceramic biological media should be left alone for months and only rinsed gently when flow noticeably drops. Activated carbon is a consumable, best replaced every 4–6 weeks if you're actively using it.

Will the heater maintain stable temperature in a 300L tank on its own?

The integrated 300W heater is sized for aquariums up to 300 litres under typical room temperature. In colder rooms or during winter, consider supplemental heating if ambient temperature runs consistently low.

Is installation different from a standard canister filter?

No — position below the waterline, connect intake and outflow, prime, and set flow, with the only addition being setting your target temperature once water is circulating.

Pairs Well With

• Master Soil – Premium Japanese Aquarium Substrate — a stable active substrate for the planted or shrimp tanks this filter is often paired with
• Chihiros CO₂ Indicator — keep an eye on dissolved CO₂ levels in a planted setup running alongside this filtration
• MasterLine Safe Water — a dechlorinator and conditioner for safe water changes once your FiltoSmart Thermo 300 is installed