I have Dolphin Nautilus robotic cleaner that always gets stuck on drain. I know there are clip-ons and unibridge drain covers, but many reviews suggest those are expensive ($70-80), not always work, and need a replacement every one or two years. Has anyone tried to solve the problem by filling a piece of hose with sand and joining the ends together to lay around the drain? What hose diameter is recommended for this solution so it is too hard for the robot to push it around?