Interesting how the lack of light would affect bacteria. Hmmm. Anyway, it won't hurt to use ChemiPure. The only thing I noticed when I first added this media was that my Coraline algae suffered a little. Some minor bleaching occurred. Could have been a coincidence. It's rebounding now. Let me know if u get similar results. Other than that, my tank seems to b more stable since I've started using it. I rinse out the media bag every couple weeks. Not sure where I read about doing that but u can c the crap rinsing out. So I think it's a good idea. Later!