@juergen_hubert
Erosion is one approach, do we know how trickling away Vs newly joining moves size?

Recruiting is a sub-class of that - make an instance designed for 10 000 mastodon.social users, tell them in waves, see them move.

Fission is a more obvious approach, where at some size the members of big instance.maybe suddenly find they are either members of biginstance1.maybe or biginstance2.maybe

You'll have to do something mildly clever with the admins of course.
#fission #fissionsocial