I've been dosing sodium silicate for last two months to get diatoms help me with LCA. Unfortunately, Dinos count in any given sample from the tank substrate beats diatoms count 10 to 1, though it's still not too bad, just some dust in the sand. However, the silica levels drop very fast. I've had drops from 11ppm to 2 ppm in 7 days (according to my Hanna HR tester) and that wasn't a unique occurrence. There are no visible sponges anywhere and I don't know what else can consume silica at that rate...
