Black Root on Phal

[Bloomer001]

Several of my Phalaenopsis orchids have a few black roots. The leaves are healthy and there are plenty of healthy roots. The orchid has a healthy spike. Light (artificial), watering, and fertilizer routine are consistent. Do you know what causes the black roots?

[estación seca]

They're older. Might have algae or cyanobacteria growing on them, which is not a problem.

[Ray]

Even if they are just old and died, they will slowly decompose, but that is no threat to the nice, new roots.

[Bloomer001]

Thanks for reply. I will leave them be