Thank you everybody for the helpful suggestions on eggshells and for the warm welcome to Speedy!
Now I have a NEW question....over the weekend I lost control and bought a black mystery snail (named "Gonzalez" - Gonzo for short). He was soooo cute, I couldn't refuse! I put him in the tank with Speedy. A few hours later Speedy finally notices Gonzo and heads over to him...he immediately slithered on top of Gonzo's shell and "enveloped" him... 8O 8O (Speedy is bigger than Gonzo). Speedy's whole body was wrapped up in Gonzo! 8O Was this enemy behavior, or...uh...um...you know???

Soon they fell off the side of the tank and landed on the gravel as "one" snail....completely wrapped up in each other.... staying that way for a looooong time. 8O
I know this sounds really naive and stupid, but should I be worried or is this just Speedy's "super friendly" way of welcoming Gonzalez??
I haven't read anything about mixing snail species....I guess I assumed they would get along. I finally managed to separat them (after 30 minutes or so) and neither one seems the worse for wear. This morning they were on separate sides of the tank looking completey normal.
Speedy's an Ivory snail and Gonzalez is a black mystery snail....I just don't want WWIII in my tank....(but babies are ok, I think?).