My Roman Arch Waterfall is not working or slowing down and not performing properly?

Most likely the water ports need cleaning. Remove the lock-ring that covers the Waterfall nozzle with ¹/₄ turn. Remove and clean the clear internal nozzle. Ensure all debris is removed from the entry points on the nozzle. For a video on this procedure, see Waterfall cleaning video. For a video on this procedure, see Waterfall cleaning video.