A google search comes up with pretty much the same info, but alot of it is vague. I know another girl who has one in her... I think it's a 10g nano, and it's doing swell. These guys aren't supposed to get big, though -- yet there are varieties of conches that do get much bigger. Maybe those are the ones you were told about?
These guys didn't make money off of the conches, though -- there was a mistake in shipment and they got too many of them. I paid $4 each.
