Let the top 1–2 inches of soil dry out between waterings
Remove any standing water from saucers and trays
Water from the bottom when possible
Replace the top layer of soil with fresh, dry potting mix or sand
Repot the plant with sterile potting soil if the infestation is severe
Remove dead leaves and decaying plant matter from the soil surface
Use yellow sticky traps near the plant
Apply BTI to the soil according to the product instructions
Use hydrogen peroxide diluted with water to drench the soil
Cover the soil surface with a thin layer of sand or fine gravel
Quarantine the affected plant from other plants
Check nearby plants for gnats and treat them too
Avoid overwatering in the future
Keep indoor compost and rotting fruit away from the plant area