Ok, please do not try this without checking it out first. Here is my story. I had this problem more then once. The first time I got these crawly threadlike things in my soil (ie. Last summer), I ended up throwing out my Thanksgiving Cactus. So last November, I purchased a few more Thanksgiving Cactus from the supermarket. I noticed those pesky tiny fruit flies/knats flying around my plants. ( they usually lay their eggs in the soil ) Well that was it! I mixed a combo of rubbing alcohol and water and sprayed the surface of the dirt on my newly purchased plants really well. I have knat/fruit fly traps all over...ie.. Near each plant. For the first time since the Fall, I recently saw the first little bugger and put out my traps. I may do my alcohol/ water spray again. But this is risky. It did not kill my plants, but it can kill them if you overdo this. Proceed at your own risk. Best to try to control this problem. I do not think you can completely avoid it if you have live plants in the home. They LOVE organic soil and there may be unhatched eggs in the organic soil you buy at the garden center to transplant your thanksgiving cactus into a new pot in the Spring. So far I have NOT transplanted anything. Nor have I fertilized anything. These tiny fruit flies/knats come in through screens or with your groceries/fruit that you buy at your local supermarket. They can even come up out of the drain in your sink! I have added photos of these traps. They work well so far for me. You can purchase them at Home Depot or True Value Hardware.

Yeah,I may be watering too much.I water everyday because the leaves look crumbled up. I dug one of them up with a spoon and it doesn't look like the bugs are on the roots or anything:They just look like they're crawling in the dirt. I did however notice a brown spot on part of one plant that looks like something has been eating on it. Also Some of the other ones I planted all popped up last nite out of the dirt and have yellow leaves.One of the plant's leaves are pale green and are dry looking. Heres a pic: Here is a link that might be useful:

Symphylans fit that description except for the length-- they're longer than one mm. Pupulations are enhanced by lots of manure. You might look up info on them to see if they fit.

Look up fungus gnat larvae to see if that's not your problem. Resolving existing fungus gnat infestations includes allowing the potting mix to dry out somewhat in between waterings ;applying a layer of food grade diatomaceous earth (DE) to the surface. It will eventually work its way into the medium, eliminating the soft bodied larvae. Some people apply a thick layer of coarse sand in order to prevent the adults from laying eggs. Rather than the imidicloprid (not the right choice) or other strong chemical, opt for Gnatrol or even dissolved pieces of mosquito dunks. Both contain Bacillus thuringiensis-israelensis, a naturally occurring bacterium which infects certain Diperans...like fungus gnats or mosquitoes. Long term fixes include changing your potting mix for one that is faster draining (very coarse textured), or amending the potting medium with substantial amounts of perlite. Of course, toss the old stuff in the pot. And evaluate your watering practices. Fungus gnats require a very moist environment in order to thrive.