The OASE BioMaster² Thermo range has quickly become one of the most popular external filters among freshwater aquarists, aquascapers, and even marine hobbyists. Combining powerful filtration, an innovative EasyClean pre-filter system, and an integrated heater, the BioMaster² Thermo offers a premium all-in-one filtration solution designed to simplify aquarium maintenance while delivering exceptional water quality.
Whether you've just purchased a BioMaster² Thermo 250, 350, 600, or 850, proper installation is essential to ensure reliable performance, optimal flow, and long-term filtration efficiency.
In this guide, we'll walk you through the complete setup process, explain how to configure the filter correctly, and share tips to help you get the most from your new OASE filter.
Why Choose the OASE BioMaster² Thermo?
The BioMaster² Thermo series offers several features that set it apart from traditional canister filters.
Key Features
- Integrated adjustable heater
- EasyClean removable pre-filter
- Large biological filtration capacity
- Quiet operation
- Self-priming system
- Modular filter baskets
- High flow rates
- Energy-efficient operation
These features make it particularly popular for planted aquariums and aquascapes where clean aesthetics and stable temperatures are important.
Before You Begin
Before setting up your BioMaster² Thermo, ensure you have:
- The filter unit
- Heater module (pre-installed)
- Intake and outlet pipework
- Filter media
- Hoses
- Hose connectors
- Suction cups
- Aquarium water conditioner
- A towel for any spills
Always unpack and inspect all components before installation.
Step 1: Choose the Right Location
The BioMaster² Thermo should always be positioned below the aquarium water level.
Ideal Placement
- Inside the aquarium cabinet
- On a flat, stable surface
- With easy access for maintenance
The filter relies on gravity-assisted water flow, so positioning below the aquarium is essential for proper operation.
Avoid
- Uneven surfaces
- Excessively cramped spaces
- Areas prone to flooding
Leave sufficient room above the filter for opening the lid during servicing.
Step 2: Familiarise Yourself with the Filter Components
Before assembling the system, identify the key components:
Filter Head
Contains:
- Motor
- Priming system
- Flow controls
EasyClean Pre-Filter Module
The removable upper filter chamber designed for quick maintenance.
Media Baskets
Contain:
- Mechanical media
- Biological media
Integrated Heater
Installed within the Thermo model to provide discreet temperature control.
Hose Adapter Unit
Connects the filter to the aquarium pipework.
Understanding these components makes future maintenance significantly easier.
Step 3: Prepare the Filter Media
The BioMaster² typically includes a combination of:
Mechanical Media
- Coarse foam
- Fine foam
These trap debris and suspended particles.
Biological Media
Examples include:
- Hel-X
- Bio balls
- Ceramic media
These provide surface area for beneficial bacteria.
Media Arrangement
Water flows from the pre-filter down through the media baskets.
For best performance:
- Coarse mechanical media first
- Fine mechanical media second
- Biological media last
This prevents biological media from becoming clogged prematurely.
Step 4: Assemble the Filter Body
Insert the media baskets into the canister body.
Ensure:
- Baskets sit level
- Media is not overpacked
- Flow paths remain unobstructed
Once loaded:
- Install the pre-filter module
- Fit the motor head securely
Check all locking clips are fully engaged.
Step 5: Install the Intake Pipe
The intake draws water from the aquarium into the filter.
Positioning Tips
Place the intake:
- Near the rear corner
- Away from heavy plant growth
- Several centimetres above the substrate
Avoid placing it too close to sand, gravel, or decorations.
Optional
Shrimp keepers may wish to install an intake guard or sponge pre-filter to protect young shrimp.
Step 6: Install the Outlet Pipe or Spray Bar
The BioMaster² allows several outlet configurations.
Spray Bar Setup
Ideal for:
- Planted aquariums
- Community tanks
- Gentle circulation
Standard Outlet
Provides stronger directional flow.
Suitable for:
- Goldfish tanks
- River-style aquariums
- High-flow environments
Positioning
Aim for:
- Gentle surface movement
- Even circulation throughout the aquarium
Avoid excessive turbulence in planted tanks.
Step 7: Measure and Cut the Hoses
The supplied hoses may need trimming.
Best Practice
Keep hose runs:
- As short as practical
- Free from sharp bends
- Neatly routed
Shorter hose runs generally improve flow efficiency.
Use a sharp blade or hose cutter for clean cuts.
Step 8: Connect the Hose Adapter Unit
Attach:
- Intake hose
- Outlet hose
to the quick-release adapter.
Ensure:
- Connections are secure
- No kinks are present
- Locking mechanisms engage correctly
The BioMaster² quick-release system makes future maintenance much easier.
Step 9: Fill the Aquarium
Before priming:
- Fill the aquarium completely
- Dechlorinate tap water if necessary
The intake and outlet should now be submerged.
Step 10: Prime the Filter
One of the standout features of the BioMaster² is its integrated priming system.
Priming Procedure
- Open the hose valves.
- Press the priming button repeatedly.
- Continue until water begins filling the canister.
- Wait for air to purge from the system.
You will often hear air moving through the hoses during this stage.
This is normal.
Step 11: Connect Power and Start the Filter
Once the filter body is full of water:
- Connect power
- Switch the unit on
The impeller should begin circulating water immediately.
Initially, you may notice:
- Air bubbles
- Mild noise
- Intermittent gurgling
This usually disappears as trapped air exits the system.
Step 12: Set the Heater Temperature
One of the biggest advantages of the Thermo range is the integrated heater.
Recommended Temperatures
Tropical Community Aquariums
24°C-26°C
Planted Aquariums
22°C-26°C
Discus Aquariums
28°C-30°C
Goldfish
Typically no heater required
Adjust the heater according to the needs of your livestock.
Step 13: Check for Leaks
Carefully inspect:
- Hose connections
- Quick-release valves
- Filter head seals
- Heater module
Any leak should be addressed immediately.
The BioMaster² sealing system is highly reliable when assembled correctly.
Step 14: Monitor Flow and Circulation
Observe the aquarium for:
Good Signs
- Surface movement
- Even circulation
- Clear water movement
Potential Problems
- Dead spots
- Excess turbulence
- Weak flow
Adjust outlet positioning as required.
Cycling Your Aquarium
Installing the filter is only part of the process.
A new aquarium still requires biological maturation.
Beneficial Bacteria Need Time
The nitrogen cycle converts:
Ammonia → Nitrite → Nitrate
Without these bacteria, fish can be exposed to toxic conditions.
Recommended Approach
- Fishless cycling
- Bacterial supplements
- Regular testing
Patience during cycling is essential.
The EasyClean Pre-Filter System Explained
One of the most popular BioMaster² features is the removable pre-filter chamber.
Benefits
- Quick maintenance
- Improved flow retention
- Reduced full-filter servicing
Typical Maintenance
Simply:
- Remove the pre-filter module.
- Rinse sponges in aquarium water.
- Reinstall.
This can often be completed in minutes without disturbing biological media.
Routine Maintenance Schedule
Every 2-4 Weeks
- Clean pre-filter module
Every 2-3 Months
- Inspect impeller
- Clean hoses if necessary
Every 4-6 Months
- Service main filter media
- Check seals and O-rings
The EasyClean system dramatically reduces how often the entire filter needs to be opened.
Common Setup Mistakes to Avoid
Positioning the Filter Above the Aquarium
The BioMaster² must sit below water level.
Forgetting to Open Hose Valves
A surprisingly common issue during first setup.
Overpacking Media
Restricts flow and reduces efficiency.
Running the Filter Dry
Always ensure the filter is properly primed before powering on.
Ignoring Air Trapped in the System
Most startup noise disappears naturally once air is purged.
Which Aquarium Sizes Suit the BioMaster² Range?
BioMaster² Thermo 250
Suitable for:
- Aquariums up to approximately 250 litres
BioMaster² Thermo 350
Suitable for:
- Aquariums up to approximately 350 litres
BioMaster² Thermo 600
Suitable for:
- Aquariums up to approximately 600 litres
BioMaster² Thermo 850
Suitable for:
- Larger aquariums with heavier stocking levels
Always consider livestock load when selecting filter size.
Final Thoughts
The OASE BioMaster² Thermo combines powerful filtration, innovative maintenance features, and integrated heating into one of the most user-friendly external filters available today. By following the correct setup procedure, you'll maximise filtration efficiency, simplify maintenance, and provide a stable, healthy environment for your aquarium inhabitants.
Whether you're building a high-end aquascape, a planted community aquarium, or a larger freshwater display, the BioMaster² Thermo offers a premium filtration solution that can support your aquarium for years to come.
At Charterhouse Aquatics, we stock the full OASE BioMaster² range, along with replacement media, spare parts, pipework, and maintenance accessories. If you need help selecting or setting up your filter, our team is always happy to assist.
