black flies in fish tank

Question
hello. my dad has recently set up a tropical fish tank and is having trouble with these black flies appearing in the tank. what are they and where are they coming from. is there anything my dad can do to prevent them.  

Answer
Dear Stacey,
Are these truly flies or some type of gnat? Maybe, they are attracted to the light as many bugs are, and that is why they are appearing in the tank. If you have recently added plants they could have been in the plants.  Keep the tank really clean by vacuuming the gravel and doing frequent water changes to help control any that are in the water.  It is possible they could be attracted to moisture that is sometimes in the aquarium hood and sometimes algae will even be growing in some areas that bugs can be attracted to. Observe and see if any of these things could be happening. Best of Luck!
Karne