Archive logging not cleaning up pg_wal directory

I have the following in my postgresql.conf for archive logging:
archive_command='test ! -f /var/lib/postgresql/prod_archive_logs/%f && cp %p /var/lib/postgresql/prod_archive_logs/%f'

This command is properly copying the log files to my archive directory but they remain in the `pg_wal` directory after they are copied, consuming hundreds of gigs of space.  Am I supposed to create a cron job to clean out the `pg_wal` directory periodically (keep only 1 day of logs I guess?)

I tried to use mv:
archive_command='test ! -f /var/lib/postgresql/prod_archive_logs/%f && mv %p /var/lib/postgresql/prod_archive_logs/%f'

When I did this the archives were moved away to the archive directory but when I tried to set up replication the server could not find the archived log to replicate from so I changed it to "cp" and now have this problem.

What am I missing?

Regards,

--Justin