The main problem with Juwel filters is that a lot of sludge and gunk is able to build up inside the filter casing due to the by-pass system. Because the filter casing is fixed to the glass it is difficult to get to this gunk and if it goes unnoticed can lead to sudden massive rises in nitrate, pH crash and overload of dissolved organic solids. The best way to deal with this problem is to stick a hose down inside both compartments of the filter casing (after removing all media) and suck out all the sludge, but this is fiddly and awkward. Its far easier to cut the juwel filter out, toss it in the bin and use another more user friendly and reliable filter.
