Hello,

I am a relatively new Oscar and aquarium owner and I love them. I have two 7 inch Tigers in a 75 Gal tank which grew from 2 inches. I will need to upgrade soon (I know).

I am having an issue with my tank and wasn't sure where to post this question.

Under my lid I have flies breeding. They are a very small Gnat like fly. They seem to gather under the lid where water condensation forms. I wipe it off constantly, but the Gnats seem to come back.

Where do these come from and how can I get rid of them?

Thanks for replies in advance.

Welcome to the site. Never seen this before. I've had flies buzzing around my tank, but never hordes of them. Don't suppose there is much you can do really. I'm not really an expert on pest control. I wouldn't have thought they would cause any harm, in fact the Oscars would probably eat them if they fell into the water

Yes... I thought it was quite strange as well. My tank is actually in my office, so it has become a bit of an issue.

I found another site discussing this, so I guess I am not completely alone on the topic. Here is the link:

badmanstropicalfish.com/forum/index.php?topic=3058.msg30058

I have cleaned the entire lid, cleaned the tank, cleaned the filters and tray, as well as an extensive gravel cleaning and water change as were suggested in the above blog.

There still seem to be a few flies that come backs.

Could these be possibly coming from the frozen blood worm larva that I have feed the fish?

Any other thoughts?

Cryogenics? No I don't think so. Once those bloodworm are frozen, they're not going to come to life again. I'm just guessing really but I would imagine the flies are probably attracted to the tank because it's warm and damp and may contain small particles of food.

I went to that website you mentioned, I was going to mention it before but didn't want to patronise you, using any kind of insecticides around the fish tank is a very bad idea.

I would just keep it clean for a while, wipe it down every day and see if the flies start diminishing

I will try that. That you for you help!

Whatever they are they must be laying eggs there for a reason. The warmth is probably one reason but another is that there is some food there. I would clean the lid and all around the glass above the water line and any cover glass thoroughly every 3 days or so till they are all gone. Dont use any chemicals tho as these might be bad for you oscar.