Hello, noticed no one replied to this thread so I thought I would. I can only share my experience with you, as you said there is alot out there on this subject and depending on who you talk to you will get different answers to the question. I had a uv sterilizer on the tank I have running now when I set it up the first time, I never had any issues with it and it did not cause any adverse effects. I set up this tank again after a year break and I did not put the uv sterlizer on it, the only reason is that I dropped it and broke the quartz sleeve inside of it and I am just too cheap to order a new unit as they do not sell that sleeve insert(figures right). I have not noticed any difference from using it and not using it. The only thing I would use it for if you have one is if you have a breakout of something and once that is rectified I would turn it off again. That is just my opinion, it does kill everything that it comes across when that light hits the water stream.....good and bad. However the amount that sterilizer is doing its thing with is small compared to the entire volume of the tank and there is no way that you are going to kill off all of the good nitrifying bacteria the filter is producing all day long in the sump. Just my opionion again. Hope this helps you in your decision.