Yes, it's inline. I was not convinced either (which is why I was content to leave the bulb burnt out the last several years). But my experience over the last week has profoundly changed my mind. Normally when my nitrates get up to 15 ppm or so I experience a cyano bloom. This weekend, still unable to reduce the bloom, I replaced the bulb and my cyano disappeared overnight. I checked my nitrates at that time and they were 20 ppm. I'm just shaking my head that I have nitrates at 20 ppm and no cyano. That's unheard of for my tank. I am glad of this because I want some nitrates for coral growth, but I wish cyano didn't come with. So far this has been a great solution for allowing me to have some level of nitrates without accompanying cyano. The caveat is if it inhibits the purple/blue stuff I wish would compete better with the cyano.