Maybe try a lighted sticky fly catcher, my tanks caused a mosquito problem a while back and that solved it
I personally have fruit flies in the house some times. I believe they are from fresh fruit such as banana. The flies hitch a ride from the grocery store.
The only thing I can think of is to find the source and go from there, it could be anywhere. Just because they’re near the tank doesn’t mean that’s where the source is. They may just be attracted to the tank and coming from somewhere else
… they’ve followed me to 5 different locations. Very annoying and endless IMO… only sure way to get rid of em is ditch ur tanks then battle em in the home drains. They have mosquito like larva laid in water and they dont need much to survive. Ive popped off sealed canister filter lids and had em fly out . Goodluck! U might be able to curb the issue with only 1 tank in house. Ive always had multiples so its a losing battle. They subside a bit themselves in the winter months.Unfortunately, this seems to be what I’m experiencing. WIth that said, they are not anywhere else but in/around the fish tank and filter. They tend to stay stuck on the underside of the glass tank lid, and do fly out whenever I open the lid or remove the filter lid. I now keep a towel over the top of the tank to keep them contained to the tank and not fly around the house.If there black and resemble tiny moths there about impossible to get rid of. Problem is there probably already in ur tank and or filter and you can’t really treat that. Vinegar/baking soda can be used to douse every house drain in. This will mitigate ur issue. Ive dealt with these suckers for about 20yrs now while keeping fish
