The thing to keep in mind about nematodes is they are very temperature, moisture and light sensitive. Make sure you read up on proper application for best results. I don't want to promote any specific companies but some are more reputable than others when it comes to shipping and vitality of stock. They definitely should come packed with enough ice packs to keep them cool and most likely be sent overnight or next day to ensure survival. Nematodes listed from an Amazon warehouse will be as effective as snake oil.
Ladybug larvae (the larvae are the bio-control more than adults) may possibly help if you have the mites on the foliage but a predatory mite will be much more effective (different species for both foliar and soil uses). I believe Amblyseius cucumeris would be the go-to choice for this type of mite on foliage, but shouldn't be necessary. Typically these mites aren't really a foliar pest but seeing them on your leaves can be an indication of a serious population imbalance in your soil. It's just my opinion but in my experience regardless of the pest, lady bugs (imported at least) are almost never an effective control. Lacewings, Predatory mites, and predatory wasps are all much more effective for pests in the foliage.
On the subject of fungus gnat larvae, it's possible you do have fungus gnat larvae and a natural predator is controlling them before they pupate. Fungus gnats and mold mites go hand in hand as well, and the mites can even hitch a ride into your garden via intruding fungus gnats. They both thrive in the same environmental conditions as well. As for the tiny microscopic worms, it's possible you're seeing nematodes as well, but I did see at least a few fungus gnat larvae in your video. You might be right about them not being fungus gnats, but populations can take off rapidly so just because you saw only a few fungus gnats before doesn't mean you aren't about to see a lot. Regardless, good luck and hope you get it figured out!
Keeping it Bodhi related :
Space Monkey around week 8
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Sunshine Daydream
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