Honestly I would not add neem, I believe depending on how much is added it can kill good microbes as well. IT may be from a plant but remember, plants contain toxins as well.
I believe the reason you have gnats is in fact because your leaving the food on top instead of burying it, well that would possibly be fruit flies, the gnats can be from your soil that you may have added. Now to answer your questions I was surprised that the link you provided from WSU said it was better to put it on top. actually to be honest I did not see where it said that myself... Any blogs, most sites, and all the worm books you read will in fact tell you to bury the food in the soil. Why? mostly because of the smell but also because of fruit flies and gnats.
The food will not promote anaerobic conditions I can guarantee you that, The worms and everything else create space in the worm bin promoting oxygen flow. especially if you have newspaper,cardboard, perlite, pumice etc. Anything that is used for aeration. Things would have to get pretty bad in order to promote anaerobic conditions. There would have to be no way to promote oxygen at all. And worms do provide oxygen by tunneling.
Your not gonna get bad bacteria growth and what would be bad if any would be very minimal. again unless you made it into a swamp and had it sealed off its not gonna go anaerobic. Think Peat bogs, those are anaerobic. I guarantee you read most all the worm books they say to bury the scrapes. Again this is where your gnat problems are coming from. Soils, think of it in this way almost all soils promote oxygen exchange, everything up to compacted clay.
You are right that scrapes will add extra moisture as they decompose, but its not enough to thoroughly wet your medium enough to promote anaerobic conditions. Worms prefer scrapes that are already decomposing because it is easier to digest, remember worms do not have teeth they used the grit of the medium in their digestive tract along with the bacteria in their digestive tract in order to break food waste down. I think you may have somehow misinterpreted aerobic conditions with the burying of food somehow, not sure how but I think you have, however if putting the scrapes on top work for you by all means go ahead and keep doing so as long as it works for you.
Now for the mites. You have to remember that mites are not bad, even if they seem to be taking over a worm been, they are a very important part of the soil food web! and the ecosystem. The only bad mite is the very fast moving red ones. And most likely the red mites you may see in a worm bin are not bad. The ones I speak of are parasite mites, the way to tell is they attach themselves to the worms themselves (that are still healthy and very alive) and suck on their blood and fluids. They do the same to worm eggs. ALL other mites that you will see in a worm bin are good, they help breakdown food scrape, decompose and eat dead worms and and sickly worms, but they do not eat healthy live worms. They will not kill your worms no matter how overpopulated the mites get. The way they will kill worms is by out-competing your worms for food in breaking it all down. This will decrease your worm population due to minimal food, not because they are physically killing the worms themselves. If the sight of to many mites is to much you can remove them by placing in squash rinds and watermelon, or cantaloupe rinds which they seem to love. Leave in overnight and in the morning remove after they have mostly all congregated on the rinds and repeat until you have significantly depleted the mite population.
The reason for the mite population would be they prefer and like moist environments, and also certain food sources such as cucurbits, including squash, melons, etc. they also love acidity, so adding tea bags, leaves, and coffee grounds will attract them as well. Adding calcium such as eggshells,lime will also help to cut out the acidity. BUT please remember that mites are not bad and apart of the food chain. It is very normal to have them in a bin. I diverse ecosystem or food web is essential. Just think of a garden or even compost where mites are common. Compost gets hot and composts for a reason. When it gets anaerobic is when it no longer breaks down organic matter. The mites are shredders and help with decomposition.
Ok. I think I tried my best to explain things lol. let me know if I forgot to address anything.
The reason I was surprised with WSU being your source without putting myself out there to much... is because I in fact do go to WSU. Again I did not see where it said that when I read through the link.
Happy worm farming!
