The OASE BIOSMART pond filter system is extremely efficient and easy to maintain.to clean the sponges all you do is pull up and dowm on the blue handles this loosens the sludge which falls to the bottom then you pull up the waste gate to release the dirty water.onto the garden or down the drain. Comes with a OASE VITRONIC 18 w uv clarifier to keep your pond water clear of green and your water healthy.a new bulb has been fitted for sale. Sponges are in excellent shape. Suitable for ponds up to 36,000 litres
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