Suction holders are indispensable for aquarium owners. They are used in many different ways to fix pipes, hoses and even technical devices in place. The plastics have been selected so that they do not release any toxic or harmful substances into the aquarium water and so that they remain flexible and are slow to harden.
Nevertheless, EVERY suction cup loses flexibility over time and will need to be replaced. The better the quality of the cups, the longer they remain flexible!