Help me identify this small black insect pest

[Grim Tuesday]

These small black insects were hiding under the "soil line" in my chysis bractscens and went crazy when I watered it. They don't seem to be occupying the leaves, rather an area of decomposing old roots, or new roots maybe? Any idea what they are and how I should treat them? My first guess is aphids but let me know if someone knows more please!