Yes, and quite quickly
because of the liquid
see: Why_serve_lemon_with_fish
maybe put some lemon juice on the fish,the foxes will not like the smell or taste of the lemon juice:)
Put some lemon juice on the rim of the glass.
it is a chemical
yes you can put a glass sheet over the top of a tank to act as a lid.
it will die
The Fish will die.
the fish will DIE!!
You die.
Of course you CAN. Whether or not you should is a different matter entirely.
24hrs or your fish will die or put age resting and then you could put them in after a hour