it seems like such an obvious question and i don’t believe that it hasn’t been asked. How do we know if we have diatoms and which ones do we have. The RO water doesn’t contain diatoms. The tap water is treated and doesn’t contain diatoms. If we don’t have diatoms living in our tank then nualgi is only feeding nuisance algae right? Nualgi is making the assumption that everyone already has diatoms living in their tanks.