BioPlus Thermo 200 Internal Corner Filter by Oase (UK) LtdBioPlus Thermo Internal Corner Filter with HeatUp. The BioPlus filters are practical internal filters for aquariums from 50 to 300 litres in size. The compact filter unit can be easily removed for cleaning while leaving the pump unit in place. The filter foam can then be replaced modularly, ideal for time delayed cleaning that is gentle on bacteria. The integrated diffuser nozzles provide uniform surface movement, oxygen enrichment and helps to