My smallest tank has been running for over a year now. The inhabitants have not changed, my cleaning methods have not changed. The water parameters are great and the feeding schedule is normal. But for two weeks now (since I changed out the filter pads) I have been getting literally hundreds of tiny flies on the glass cover under the light. To be clear, they are appearing on the underside of the lid, directly under the light where the water hits from the air stone. I wipe them off twice per day. Did a massive water change. Cleaned all plastic plants, scrubbed the walls of the tank and cleaned out the filter itself but they just keep appearing. I can only guess there were eggs on the new filter pad, but has anyone else seen this before (it's definitely a first for me)? Also, any other ideas of what I can do to get rid of them?