Can anyone help? I have had a pond in the garden for a number of years. Use a pump to push the water through a UV filter, then back into the pond. I bought a pump a few years ago. Initially it gave a good flow rate but lately the flow has dropped quite a bit. I have taken it out and cleaned it but that has made no difference. Do these pumps slowly give up the ghost over time or should they last indefinitely? Do I need a new pump? The pump is a Blagdon 5000.