An o-ring is a thin gasket seal. In aquarium equipment, an o-ring or gasket is often used in a filter lid or pump housing to prevent water leaks. Over time, o-rings and gaskets deteriorate, often causing leaks. Before replacing an o-ring or gasket, look for any small debris that may be breaking the o-ring seal. Also, be sure to use an o-ring lube like silicone lubricant to prolong the o-ring life and secure the seal.
Gaskets & O-Rings