yes, you should clean your bio-falls. Acutally it is much healthier for your pond to clean it several times during the summer instead of once a year. you will be amazed when you see how much gunk is in there. Rinse it very well in pond water or dechlorinated water. do not use city water or the chlorine will kill the bacteria. I sometimes take the media out and rinse it gently in a tub of water to get it clean. don't use a high-pressure hose....the idea is to get the gunk off without disturbing the bacteria layer. the bacteria is pretty well attached (especially to the lava rock) so don't worry about it too much about knocking it loose. It will be fine.

Tracy, are you in zone 5? Then, after you do the rinsing, and you throw the WH out, you can sink the media to the bottom of your pond for the winter. With a piece of string tied to the bag. Then you can haul it back up in spring and put it right back into the waterfall, bacteria and all. Works great for us.

Btw, our lava rock came in a mesh bag, and the bag has a hard time with the weight. So we replaced the lava rock with pot scrubbies from the dollar store a few years ago, this is much easier on the mesh bag - as well as on the shoulders! - and we only use a few pieces of lava rock to stop the mesh bag from floating up.

:) Mary

Thanks for the advice. I noticed that there is a lot of gunk in there. It's pretty nasty, but I was told not to clean it too often so the "good bacteria" stay. I'll clean it this weekend. Yes Mary, in zone 5. I was going to leave it running because we've been having very mild winters.