Several things come to mind that may help. Do you use a pond net to
reduce the leaves in the pond? Are you using a skimmer to stop the
waste from reaching the pump? Is it possible to use an out of pond
pump? Using a very strong air pump is very important to keep the pond
oxygen levels up all year long. Using ML O2 is a good start. I have
several articles on pumps on Richdeer3pondsupplies.com ( copy and
paste)

I rarely have to clean my pump even with 2 elms overhead. I have the
pump in the bottom of a plastic flower pot with a old round dehydrator
screen on top. It also water to flow in and the filter media doesn't
clog. Matala filter mats do not clog or channel like other filters.
They can be cut to fit any filter and come in 4 densities. Filter
brushes are a good option too.

The reason that the intake hose is smaller then the discharge size is
that restricting the outflow can over load the pump motor. I have
solved the multi sized hose problem by going to the farm supply store
and buying bulk plastic tubing and cutting it the size. Heating any
hose in hot water will straighten it out and make it fit over even
the snuggest fit. Algae can be cleaned out of hoses with hydrogen
peroxide left in several hours.

Good luck and email me if you have any questions or need help finding
a product that will work for you. Gail at http://www.Richdeer3pondsupplies.com
email or call 641-750-3062