That's means its working.
This is what I saw:
Why would I recommend dosing silica? Largely because creatures in our tanks use it, the concentrations in our tanks (at least in mine) are below natural levels, and the sponges, mollusks, and diatoms may not be getting enough to thrive.
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Figure 3. A view of the inside of the front glass of my reef tank 5 days after scraping the glass.
Figure 6. A view of the inside of the front glass of my reef tank 5 days after scraping the glass and adding the silica supplement.