Those tiny bugs you see flying around your bath drain are drain flies, also referred to as moth flies. They are attracted to moist, highly organic areas such as sink drains, storm drains, sewage treatment plants and rotting vegetation. While these insects do not bite or sting, their presence can become annoying enough to require action. Regular cleaning of your bath drain as well as cleaning any other areas of the home where standing water accumulates will remove these pests and prevent them from returning.
Clean any areas inside and outside of your home where you find stagnant water and slime with baking soda and white vinegar-water solution. Use 55 to 110 g (1/4 to 1/2 cup) of bicarbonate of soda depending on the size of the stagnant water pool. Create the vinegar-water solution by using a 59 ml (1/4 cup) of vinegar for every cup of water used. Clean with bicarbonate of soda and the vinegar-water solution separately or mix together to make a foamy paste. These areas are breeding grounds for drain flies and other pests, so eliminating these sources will help prevent drain flies from coming back.
Pull out drain hair, and use a wire hanger to grab hair that is farther down the drain. Clean your bath drain thoroughly with bicarbonate of soda and white vinegar-water solution using the same measurement guidelines from Step 1. Scrub with long, thin brushes, such as wire drain brushes or old toothbrushes, as far down the drain as you can. You can use a drain snake -- a device that winds down a drain to remove clogs -- if necessary.
Use caustic or organic drain cleaner if necessary to break up excess slime and mould. Pour drain gel down your drain at night and plug the drain with old rags.
Clean and freshen your drain each week by pouring 136 g (1/2 cup) salt, then 110 g (1/2 cup) bicarbonate of soda, then 237 ml (1 cup) vinegar down the drain. Let this solution foam overnight if possible, and then flush with boiling water. This will keep scum from building up and the flies away for good.
You can use a plunger to push remaining scum and debris down the drain. Pour bleach down the drain as another method of cleaning.