[Burks]

A friend of mine has been keeping Corydoras for many years, if not decades. He uses them in his bare bottom Guppy tanks to clean up uneaten food, and to breed them on the side.

Over the past month he has noticed his Cories are starting to lose their barbells. They still eat and act normal I guess.

Any ideas what might be causing this? They've been in the tanks for many months and have even bred.

Thank you.