Not sure what you mean here Tom, usually when one bulb goes the other is ok :? Not familiar with Juwel the one I had only had one tube. On my current tank each tube has it's own ballast and switch so when a tube goes the others still work. I'm guessing here that your tubes share one, in which case there should be no reason why you can't just cut one of the tube out of the circuit as long as you blank the ends of the cable off properly and make sure their water resistant.