Substrate critters

I just noticed that in my 20 gal planted tank the gravel substrate is
populated with thin reddish worms, about 1.5" long. I guess they might be
the descendants of the blackworms I fed my fish with more than a year ago. I
can see them only at night, with a flashlight, at all levels of the
substrate (~ 2.5" thick). I would think they do a decent job in aerating the
substrate, and I have not been noticing any sign of damage to the plants,
which are growing quite well. I read in the past of the possibility of
infestations of substrate with blackworms, but I never heard of direct
experiences in planted tanks. Has anyone else observed a similar situation?
Could it become one of this optional recommendations (like trumpet snails)
to keep the substrate "alive" and provide healthy snacks to the
bottom-dwelling fishes?