This one has me scratching my head. I have a 3 y/o, well established 14g BC that has suddenly started showing what I believe are diatoms. A brown “dusty” growth, mostly on the glass that is easily removed with my algae scraper. It's definitely gotten worse since I shut down my skimmer, but I'm trying to re-establish some nitrates for my zoas, so starting the skimmer back up, or adding something like Purigen would have a negative impact on that effort. The only new addition, a month ago, is a small frag of Candy Apple zoas, and this started showing up shortly thereafter. I’m aware they feed off silicates in a new system but unless the very small frag was absolutely crawling with silicates, I’m at a loss as to where it could be coming from. I suppose it could be another form of brown algae, but it certainly appears to be diatom's. I'll post a pic or two today once the lights come on. Ideas, gang?