What are these small black bugs?
 

These are VERY small, I don't think they're aphids, and they're only on the root system. Are they some kind of springtail or microfauna? If they are obviously I don't mind but I want to make sure they're something not serious. This is a prosthetcha and it's actually been doing very well the past month with loads of new roots and a new growth. There are no bite marks or anything.

Obviously there isn't enough detail to be sure, but based on what I can see, if I saw these on my plants I would be confident they were springtails and not worry about it.

The general shape of them isn't typical for springtails, but look more like Psocids, aka book/bark lice. They feed on decaying organic material and enjoy moist environments, and won't harm the plant. Depending on how old the medium is, they can be a sign that you should consider repotting soon.

That being said, without a better photo (which is very difficult to do given the size of the insect) it hard to give a definitive answer.

Thanks for replying. The medium is LECA and sphagnum and is kept fairly moist. they're about the size of springtails but black. I'll leave them where they are as I'm sure they're doing a good job and if they're like springtails they won't leave the environment.

Don't look like springtails to me, I agree with Camille. I have some occupants in my plant as well, but if I don't see signs of damage I let them be.

For those who think these don't look like springtails, perhaps you are not familiar with Globular Springtails, order Symphypleona.

[URL="https://www.inaturalist.org/taxa/152965-Symphypleona/browse_photos"]

I've never heard of them, and they are soo adorable and cute looking!