Back in the hobby after long absence.
I see many open tanks on this site, and indeed, the tank I'm setting up, a Nuvo Fusion 20, has a screen top, for all intents and purposes an open tank (does keep the critters from jumping out). Back in the day, open tanks were frowned upon because of stuff getting into the water from the air. I wonder what's changed in the thinking of aquarists. I know of course that there are still plenty of canopies and hoods still out there.
What about it? Do you worry about atmospheric pollutants?