External aquarium filters

An external aquarium filter sits under the cabinet: it provides mechanical and biological filtration without cluttering the tank. Here you will find OASE BioMaster 250, 350, 600 and 850 external filters, in the standard version or BioMaster Thermo with built-in heater, as well as JBL CristalProfi, Sera and Superfish external filters. Our aquarium and pond experts have been advising you since 1998, with delivery to France and Belgium.

Which OASE BioMaster for my aquarium?

First choose the model according to the volume of your aquarium. The figures below are taken from the OASE BioMaster² product pages.

• Volume: start from the actual volume of your tank, then take the stocking level and organic load into account.
• EasyClean pre-filter: every BioMaster has a pre-filter chamber that can be cleaned without opening the whole filter.
• Media: biological filtration with Hel-X and filter foams, supplied with the filter, as are the hoses and the inlet and outlet pipes.
• Freshwater and saltwater: BioMaster filters are suitable for both.

BioMaster or BioMaster Thermo?

The BioMaster Thermo has a HeatUp heater built into the filter: no more heater visible in the tank. Its power (150 to 400 W depending on the model) is in addition to that of the filter. On standard BioMaster² filters, the HeatUp module can be added later if needed. Before buying a spare part, check which generation your filter is (BioMaster or BioMaster²).

Installing and maintaining your external filter

Respect the maximum head height shown on the product page, the hose diameter (16/22 mm on BioMaster filters) and the filling instructions: the BioMaster's purge button makes priming easier. Unplug the filter before any work and protect the biological filter bacteria: rinse the media in water taken from the aquarium.

Frequently asked questions

Which BioMaster for a 300-litre aquarium?

The BioMaster 350, designed for aquariums up to 350 litres. If your tank is heavily stocked, look at the next model up.

What is the difference between BioMaster and BioMaster Thermo?

The filter volume and flow rate are the same; the Thermo version also has a built-in HeatUp heater: 150 W on the 250, 200 W on the 350, 300 W on the 600 and 400 W on the 850.

What is the flow rate of a BioMaster 850?

1,550 L/h maximum, for aquariums up to 850 litres, with 8 litres of filter volume.

Does an external filter replace water changes?

No. Filtration does not remove all dissolved nutrients: adjust water changes to the measured parameters and the tank's stocking level.

Also see our internal aquarium filters, our filter media and our water quality tests.