Oase BioMaster Thermo External Filter (250/350/600/850)

Tell us about a better offer

Enter all the details of where you have found the product cheaper and if it’s legitimate we will send you a voucher code to buy the product at the cheaper price. Please ensure you include a valid URL. You will receive a notification via email within 48 hours to let you know if your price match has been accepted. Terms and Conditions apply, click here to view.

Oase BioMaster Thermo External Filter (250/350/600/850)
Ask us about this product

Find Your Nearest Store by location or postcode

And/or by Store Specialities

Search for a store by specialities


Oase BioMaster Thermo External Filter (250/350/600/850)

Oase BioMaster Thermo External Filter (250/350/600/850)

  • BioMaster 250 for aquariums up to 250 L
  • BioMaster 350 for aquariums up to 350 L
  • BioMaster 600 for aquariums up to 600 L
  • BioMaster 850 for aquariums up to 850 L
  • Space for Aquarium Heater (included)
  • Quiet and energy-efficient
  • High filter capacity with Hel-X and sponges
  • Suitable for freshwater and saltwater aquariums
  • 3-year warranty

Oase BioMaster filters are engineered in Germany for the most rigorous requirements. These external filter meet the highest demands in water filtration and filter cleaning. The combination of highly effective biological filtering with Hel-X and mechanical/biological cleaning with filter sponges ensures healthy and clear aquarium water. The BioMaster is suitable for aquariums with a volume of 250 to 600 litres.

No complete cleaning needed: the EasyClean pre-filter chamber enables convenient filter cleaning. The automatic shut-off and safety lock prevent unwanted water leaks, e.g. when removing the pre-filter module. A practical venting button makes the water suction highly effective and allows for a quick and convenient start.

The complete set includes filter media, hoses, adapters, suction and discharge pipes as well as the water diffuser. The BioMaster Thermo comes with an adjustable heater.

Key Features

Quick and Easy Maintenance
The EasyClean pre-filter module means no more bothersome removal of the filter, the pre-filter module is simply taken out, rinsed out and reinserted. The unique shut-off automation and safety locking mechanism prevents undesired water escaping when removing the pre-filter module. The vent button for effective water intake, giving a fast and easy start up when installing and after cleaning

Chamber for Heater
The included HeatUp adjustable heater has been designed alongside the BioMaster thermo to fit perfectly into a slot in the unit. This leaves the top of the heater protruding from the top so it can be adjusted to the correct temperature without having to open the filter canister. 

Large filter volume
The combination of highly effective biological filtering with Hel-X and mechanical/biological cleaning with filter sponges is ideally coordinated to ensure healthy and clear aquarium water. The water flows through the pre-filter first, ensuring an extra long service life.

250 350 600 850
Aquarium Volume Up to 250 L Up to 350 L Up to 600 L Up to 850 L
Flow Rate 900 L/H 1100 L/H 1250 L/H
Power 14 W 18 W 22 W 32 W
Max Head Height 1.3 m 1.4 m 1.8 m 2.2 m
Product Dimensions 24 x 24 x 37 cm 24 x 24 x 42.5 cm 24 x 24 x 48 cm 24 x 24 x 54 cm
Heater Included 150 W 200 W 300 W 400 W

No one has left a review yet.


Delivery costs for your order will be calculated during the checkout process based on your delivery address and the contents of your basket. You will only pay one delivery charge for your order. Express delivery is FREE for online orders OVER £39 unless any of the points below become a factor.

  • Some large items like aquariums, ponds and pond liners will have an additional charge of £45.00 to help offset the cost of a pallet delivery.
  • Orders containing a physical gift card will have an additional charge of £2.45 to cover the cost of materials and delivery (digital gift cards are a free alternative).
  • Orders to highlands, islands and Northern Ireland may incur an additional delivery charge displayed at checkout this is based on the postal code provided. DPD provides a list of postal codes which have additional surcharges. Some of these post codes may also take 2 working days to arrive, even on express. Pallet deliveries cannot be sent to these post codes.

We only ship to the UK and cannot ship internationally.

We aim to dispatch items that are currently in stock on the same working day if they are ordered before 2.45 pm (excluding Bank Holidays). Orders after 3pm will be dispatched the following working day, unless it fits any of the below criteria:

  • Orders containing live plants will take up to 2 weeks to arrive. We take a week's worth of customer orders and then inform the plant farms of the specific quantities we need to fulfil that week's order to avoid wastage.
  • Pallet orders containing large items like big aquariums will take additional time to arrive as they are sent by a third party. These orders will NOT be dispatched until we have been in touch to arrange a delivery date, this is to ensure someone is available at your address to sign for the delivery. Deliveries will generally be delivered ‘curb side’ within the terms of the agreement we have with our couriers so you will need to make arrangements to transfer larger items into your home yourself. Unfortunately, our drivers are not insured to transfer the aquarium into your home.
  • Physical gift cards and items from the gift shop (such as clothes, towels etc) are sent with 1st Class Royal Mail. Delivery usually takes 1-2 working days, though in rare cases and orders placed closer to public holidays (Christmas, Father’s day, Mother’s day etc.) may be longer.


If you are not 100% satisfied with your purchase online from our website, you can return the product and get a full refund or exchange the product for another one, for up to 21 days from the date you purchased it.

We strongly suggest signing up for an account with fishkeeper.co.uk as this will allow for some additional returns options like return to your local store.

If you checkout as a guest you will need to return the product to Maidenhead Aquatics, PO Box 619, Egham, Surrey, TW20 2BS, please package the order (along with a packing slip or a note including your name, address and order number).

Large pallet items like aquariums are deemed delivered successfully with no damage once the the driver has left the property. If a report of damage is submitted after the driver has left we may be unable to assist with replacements. We recommend refusing a damaged delivery, this is the fastest resolution.

Our full terms and conditions can be found here. When you place an order with us online you are agreeing to these terms and conditions.

For delivery before Christmas, orders must be placed on or before 3pm on Wednesday 20th December. We cannot guarantee delivery of these orders pre-Christmas as we are reliant on our couriers, but will use our best endeavours to get orders placed on this date out to you before Christmas. For full details of our festive delivery and opening times click here

Please note: online orders placed after 3pm on Friday 22nd December will not be dispatched until the New Year. For full details of our festive delivery and opening times click here