o) Prothalli with fronds: seperate them in pots. In my community are
several links about soil types. But I guess if you just give a bit humus
to your sand/peat mix it would be fine (1:1:1).
o) Prothalli without fronds: as another member noted 'Vereinzelung, weil
bei zu dichter Stellung keine Eizellen entstehen, sondern nur Spermien.'
I would guess play prothali chess. Separate them in patches in a second
container like a chessboard. :-)