How Often Should I check the pump for debris?

It depends on how often you skim the surface of the pond and how well your skimmer works.  Do you have a submersible pump or an external pump. Submersible pumps are usually located inside the skimmer and unfortunately get clogged with debris fairly often. Leaves and algae get trapped against the small slot that protect the opening of the pump from anything (usually) larger than 1/4″ like fish, snails and fingers. Once debris clogs the intake screen the pump will have to work harder to move water, which can lead to premature pump failure therefor it is always a good idea to check the pump for debris. Heavy debris will settle near the pump if housed inside of a skimmer. When you remove the pump to clean it, it is suggested to also remove any debris that has accumulated at the bottom of the skimmer.  If this step is not performed the pump can easily become clogged again and the pump will once again have to strain to get the water it needs.

There is an impeller that spin inside the plastic housing which can also become clogged. We have seen a wide variety of  items such as snails and wood chips clogging the impeller