Product like that lower the surface energy, so the water will form tiny droplets, rather that wetting the surface, forming a thin film.
On a car windshield, the former is preferred, as the wind will blow them right off, but on a terrarium wall, they'll just sit there, making the glass harder to see through.
What you'd need is a bathroom mirror "antifog" product to do just the opposite, but I honestly don't know what such products might do to plants.
Ray Barkalow, Orchid Iconoclast
Treat Your Plants Right
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