I almost lost my tank when I had the walls in my house painted. My skimmer went nuts and the coral bleached. It recovered but it was touch and go for a while. It had to be the paint fumes in the house.
I painted the back of and the bottom of my tank,black and blue,and I never had a problem,I refinished my stand aswell,and stained it a cherry oak,I didnt have any problems.
EDIT:I did however let my stand sit outside for a good day to air out.
I stained and polyed my stand inside my house (I don't recommend it) about six feet away from a running tank with absolutely no issues. When I had the house painted the skimmer went nuts because of the dry wall dust.
i painted my room with tanks running without issue.
id imagine it would depend on the VOC of the paint.
surely oil based paints would be worse than water based
If your tank is surrounded by oil based vapor, then some of it will defintely enter the water as it settles, being heavier than air. One drop of oil can pollute 1,000,000 gallons of water, imagine how little it would take to ruin 100 gallons. I painted a room with an open top tank in it no problem with water based killz. Make sure you open a window and have a fan blowing out it.
Just a note might be safe for corals but it's still harmful for you and the children to inhale them in a closed area. I'd say paint in a well ventilated area and/or wear protective gear otherwise.