Regardless of the filter types that you use, they can and do fail. These failures come in all forms, but one of the worst is a seal failure or a hose failure on external canisters and sumps. An external filter that stops working but doesn’t leak is one thing. But that same tank losing water because of a hose, filter, or tank seal failure is something different.
If you keep fish long enough, you will eventually experience a tank or filter failure that will inevitably leave you with a floor full of water. It WILL happen.
After nearly 20 years of personally avoiding such a disaster, my luck ran out this past weekend. I woke up Sunday morning and, like every other morning, went down to the basement where all but one of my show tanks are located. The basement is partially finished and partially carpeted.