I kept some communally for a short period, before splitting them up.
As scarab mentioned in a previous thread, they are not "communal" in the true sense of the word. Limited space doesn't seem to be neccessary for them to live together peacefully as in the case of certain pokies, so a relatively large tank should work just fine for them.
I would recommend feeding them regularly to avoid cannibalism and watch for any fights starting amoungst the "community".
If you suffer a loss or 3, I would rather split them up.