I've got them in the tank now. I left them in the shell until I can figure out what to do. They were pretty well closed when I put them in and now that they've opened back up I can see I have them too close together, they are overlapping. But, I'm thinking that may work to get them to move apart - and out of the shells.
To propagate mushrooms just cut it in half like a pizza. You'll get two mushrooms in no time.
Completely in half, all the way down through the foot so that I have 2 completely seperatae mushrooms? I'll keep that in mind. For now, since I'm new at this I'll take neilster1's advice and just see if I can get them to survive before I go cutting away.