Use NotifyOSD with i3wm window manager

I use i3wm as window manager, but something seems to be broken. I want to use NotifyOSD as a notification service, but I am not able to set it as a default service. At the moment I get ugly blueish angular notofication messages in the top left window corner (maybe dunst). How can I install NotifyOs and set it as default?

Even if I use Unity as WM, NotifyOSD does not work.

I found this thread, which claims (part of) the solution is:

sudo aptitude remove --purge dunst

Edit: It works! After a reboot (login & logout may do it four you), I now have the "old" notifications in the righthand top corner back.