Under tank external filters: water flooding problems?

I am new to the group.

I am thinking about installing a filter in the storage space below the
tank. I have not yet decided on what kind of filters: wet/dry or
others. But I was wondering that, if the pump stops working, whether
all the water in the tank will be syphoned down into the storage space
and eventually onto the floor?

My only experience is an external pump hanging onto the side of the
tank.

My air pump has a one way valve which is supposed to stop any water
from syphoning off. Also my air pump is a couple of feet above the
tank so syphoning shouldn't be a problem.

I will appreciate any advice.