Although I'm not familiar with the Juwel filter I will lend you my opinion. I have never seen a filter designed to be shut off. The need to be run 24/7. The benificial bacteria in the filter require oxygen to survive. Without the flow of the filter they will quickly use up any oxygen in the filter and die. I belive the Juwels are internal filters so this may not happen. If your not circulating any water your also not getting oxygen to your fish which could suffocate them. There is also the chance that you will forget to turn it back on. Putting a filter on a timer won't work because filter sometimes won't start by themselves and need so help. I don't see any benifits to turning the filter off.