Compared to other magnets this is quite good here. It keeps well when cleaning the disc and the "floating" feature also works. However, the cleaning performance is rather poor: The cleaning page is loaded with a multitude of small, densely strung together plastic knobs which, although fairly well removed in contact with the glass debris, however, remain the small gaps left untreated. The disk is getting so little clean. I've tried to solve this problem with a thin slice einers sponge, which I pinched between the magnet and disc. This design holds thanks to the Kunstoffnoppen even very good, provlem, however, is that the magnet no longer slides on the disc, but moves only jerky and squeaky. On the one hand this phenomenon is bad for the cleaning performance, on the other hand my fish are thereby greatly startled.
My personal conclusion is that such a magnet can not replace a rod-bound aquarium cleaner.
