The coarse blue sponge is a permanent resident of the upper Bioflow insert. Its open pore structure traps larger debris while the surface area carries the aerobic bacteria that do the first stage of biological filtering. Every Bioflow runs one.
Replacing it throws away a live bacteria colony. Juwel's own rule is never to replace all the blue filter media at the same time — do the coarse and the fine sponges months apart, or the tank can effectively cycle again. Rinse the blue sponges under running water at each service rather than changing them early.
Where it goes
Bottom of the upper filter insert, under the Nitrax sponge.
Choosing a size
- Medium — Bioflow M: Rio 125 / 180 / 240 LED, Lido 120 / 200 LED, Trigon 190 LED, Vision 180 LED, and the Primo 110 LED 2.0 (which takes M, not S)
- Large — Bioflow L: Rio 350 LED, Vision 260 LED
- XLarge — Bioflow XL: Rio 450 LED, Vision 450 LED, Trigon 350 LED
Replacement
Juwel's product page says roughly every three months; the filter manual gives six to twelve weeks. A falling water level inside the filter housing means it is clogging and due sooner.
The rest of the Bioflow range is in our Juwel collection.