I installed powerline and it works fine in the normal terminal.
But when I open tmux it keeps adding status-bars at the bottom of the window every 2 or 3 seconds.
.tmux.conf only contains
This problem is described on GitHub here
For some reason, deleting the watch character in
powerline.json didn't work for me, but deleting the
"name": "time" line in the
.../tmux/default.json file removed the clock and fixed the problem.