After scanning through all the post's I have not seen any information about this. I don't have a bottom drain so I do weekly water changes by vacumming with a pond vac 3 to get the poop and debris off the bottom. I am very meticulus about doing this as I do have rocks on the bottom that are sparsley laid. We have an autofill valve installed so my water is replenished through my r/o system as well as retopping for evaporation. This is my first winter with fish in the pond so my question is: Is it okay to continue to do 10% water changes on a weekly basis? I want to keep the bottom of the pond as fresh as possible. I will also be using a submersible pump for draining so I don't scare the fish. We don't freeze over very long so the water stays open pretty much all winter but it does get below 40* F.