The Biotec 5, 10, 5.1 10.1 and BioSmart 18000 and 36000 are all ‘gravity flow through’ pond filters and have considerable filtration surface due to the specially developed filter foams. It’s important to use genuine OASE sponges and not non-branded replicas foams as these will not offer anywhere close to the same surface area and are also likely to block quicker, meaning far more frequent cleaning. We also stock spare filter foams and replacement sieves for the new BioTec Premium 80000 Automated Drum Filter. The micron mesh sieves fitted to the drum filter can be easily cleaned with a solution of kettle descaler or the OASE PumpClean fluid if these block up over time and the sieves only need replacement if these are damaged beyond repair. If you have a specific spare part you need for your BioTec or BioSmart filter and you cannot find it on our website, just drop us an email or call and we’ll order it in from OASE Germany for you. Delivery is usually 5-7 working days if the item is not in our stock.