I made this bog filter for my fish pond a few years ago without knowing if I was doing it the correct way or not. It seems to work reasonably well but the polyester filter still needs changing every 6 months or so, which I assume would be normal. I just have a submerable Anyone who has more experience than me welcome to comment or give advice. I have a submersible pump that pumps the water into the bowl where it's filtered through the polyester. The netting is to stop fish jumping out, which a few have done over the years, it kind of spoils the look but it works.