I can’t help with flies. Just came in because I misread the OP as talking about files.
you need to hold down the shift key to get rid of more than one at a time.
If the old “Shell No-Pests Strip” is still available (the original formula was a nerve poison which didn’t care about species), you might give them a try. Haven’t seen one in years, and Shell’s name came off decades ago.
It is a strip of yellow plastic about 1/4"x3"x6" in a goldtone cardboard box foe esthetics. It is hung and emits poison into the air.
Ugly, but still worked.
I wouldn’t use anything like that around fish tanks.
sticky strips, funnel trap w/bait, find out where they are breeding . . .
If chemical warfare is indicated, about anything will cause fish casualties - they will:
Have an independent air supply for a day or 3
or
Be removed from the premises
or
Be replaced
I’d try the strips before resorting to bug bombs.
NOTE: Every few years, we get treated to another story of a house explosion caused by a bug bomb being to close to an ignition source (water heaters are the usual suspects)
If you deploy a bomb, first TURN OFF THE GAS! Even if you can’t/don’t want to re-start a pilot light, call the utility company - they will almost certainly provide the service free - they don’t want people guessing when holding a fire near an open gas line.