Myth alert --
IMHO this corydoras needing to have smooth substrate so they don't hurt their barbels is a myth.
The barbels are the first to go when water quality is an issue. I've not seen anyone who had a hurt or barbel worn corydoras who
didn't have water quality issues or brought it home from the store that way or the cory developed the problem during -- was or what should have been -- a QT period of 2-3 weeks.
Anything I've read has been "I've heard" or "a friend of a friend" type of stuff.
FWIW I've had my corydoras on Flourite -- and that ain't smooth by any means -- since day one and NONE of them have ever shown signs of damage. I check these guys at LEAST once a week for barbel damage.
NADA. Very healthy lot.
My oldest is a peppered cory that has the longest barbels I've ever seen. His name is Fu Manchu and he's always in the Flourite digging around for food. He has never shown barbel damage. He likes to swim upside down at the top of the tank and eat from my fingers, too. The barbels tickle
This is not to say that sand isn't more "ideal" for cory cats to dig around in. Same can be said for ANY fish that digs in the substrate. Kuhlies, clowns, you name it.
My 2 cents and if someone can point me at some *definite* publications that prove the cory substrate question, I'd like to read it. I don't want opinions, however, I want
facts.
Roan