Seal every gap between the net cup and the lid, keep the growing medium from staying soggy at the surface, and use yellow sticky traps for the adults. Small flies need moist surfaces and open water to breed, so closing those off breaks the cycle.
Which Flies Are They?
Tiny dark flies hovering around plants are usually fungus gnats. Their larvae live in damp growing media. Fruit flies are a little larger, often with red eyes, and come for overripe fruit or anything fermenting nearby.
Seal the Containers
Gaps around net cups let flies reach the solution and the wet medium. Use net cups that fit snugly and cover unused holes.
Choose Your Medium
Inert media such as rockwool and clay pebbles give gnats less to feed on than organic media like coco coir or peat. A thin layer of clay pebbles on top of the net cup helps the surface dry out.
Trap the Adults
Yellow sticky traps placed just above the plants catch flying adults and show you how big the problem is. For fruit flies, deal with the source: overripe fruit, compost caddies and drains.
Keep It Clean
Remove dead leaves from the net cups and clean up spills of solution. Both give flies somewhere to breed.
Related guide: growing Kratky in apartments and small spaces.
