Not a pro here, but if this helps, here's my fruit fly experience; I took up vermiculture (worm composting), following online instructions. The instructions indicated to have them live in newspaper shreddings, I don't know if that worked for anyone else, but for us it began a fruit fly issue that did spread into some of our houseplants. For one thing we hadn't sterilized the worm castings before using them, that was a definite thing that allowed the fruit flies to spread to the plants. Google search some safe ways of sterilizing compost and soil that you think might have parasite eggs in it. But to get the fruit flies out of my worm castings, I changed the system. I brought in a bucket of sand and a bucket of old dried out clay/dirt from outside, and every time I added a bucket of plant waste to the mix, I'd bury it in the surroundings, then put a fine layer of dirt and then a finer layer of sand on top of all of the mix. That made it apparently entirely uninhabitable for the fruit flies. My theory is that to lay and incubate eggs, they need specifically the surface to be moist and rotten, I don't think they do a lot of burrowing, I'm guessing their wings would get damaged. So regardless of how organic the compost underneath is, they couldn't use it as a breeding ground so long as there was a barrier of dry sand and old clay-heavy soil. After figuring that out, I always pot my plants with a drier, older, nutrient parched soil for the top couple of centimeters. Haven't had the fruit fly issue since. Sorry if that wasn't concise! I thought it might help.

I had a countertop compost container and did have trouble with it. I wasn't able to empty it every day, and (for me) even leaving it for a few days did result in smell, fruit flies and even one really gross fly larvae incident. Seems like many people have no issues with them, but I certainly did. I ended up buying this compost collector that you store in your freezer and I couldn't be happier with it. It's probably a bit on the small size for a large family, but it works well for me: no flies, no smell, and if the plastic gets icky I can throw it in the dishwasher between compost loads. It even seems to me that freezing and thawing the food scraps helps them break down more quickly, although it's possible that's just my imagination. That said, you could probably use just about any freezer-safe container for compost storage rather than buying this particular item, if you wanted to go that route. Here is a link that might be useful: Freezer Compost Collector

I've had infestations in my studio apartment and gotten rid of them. 1. Set up a trap with a small hole they can get in but often can't find to get out, some water with something to attract them (I put in a bit of rotten fruit and put saran wrap over it with a small hole.) They smell the fruit and can find the hole to get in but then can't get out. Put it near your bin. 2. Freeze all your produce before putting it in. FF eggs are often in the rind when you get them from the store. (It speeds up degradation for the worms anyway and if you're doing it for the FF eggs you don't have to feel guilty about using more electricity just to make the worms happier ;-) 3. Put a tall layer of bedding on top of the working food layer. I was told and it seems correct to me that FF won't burrow down in to something to lay their eggs. They'll only lay the eggs if the food is on the surface. I don't cover my bin - the worms need oxygen. I just have about 8 inches of machine shredded crinkled up newspaper (actually phone book). When this paper gets wet and turns in to actual moist bedding with food on top of it, it's less than a quarter inch thick, so it's not really all that much paper, but dry with air pockets it's bulky and prevents both fruit flies and fungus gnats. It will take quite a while, but it can be done. Good luck!!!

In most cases, gnats are more a nuisance of a more serious underlying problem than a threat to plants, but bad infestations can lead to root damage, as already noted. The 'more serious' underlying problem relates to soil choice and watering practices. Gnats are not usually a problem in soils that drain well or plants that are watered appropriately. For example, I water about every 4 days while plants are indoors and never have gnat issues because of the soils I use. When using more water-retentive soils, allowing them to dry down to appropriate moisture levels before subsequent waterings goes a long way toward eliminating the type of environment gnats prefer (moist and rotting plant matter). There are ways to eliminate most of the excess water that tends to refuse to leave the pot when it's only gravity putting on the pressure. For instance, after watering you can hold the plant over the sink and move it downward, then smartly reverse directions to upward. This uses Newton's First Law of Motion to FORCE water out of the drain hole every time you change direction from downward to upward. Try it - it will make a notable difference. More on how to deal with water-retentive media here. Also, a wooden dowel (5/16" diameter - from any hardware or big box store) sharpened in a pencil sharpener will serve well as a 'tell'. When stuck deep into the pot (like all the way to the bottom) and removed, it will show you when to water. If it comes out stained dark or moist, withhold water. Al