>Do you guys ever add anything to your sugar water that is used to encourage wax from the bees?
No I don't.
>Ie, have you ever put in a small amount of salt, or menthol or spearmint flavoring?
I have noticed that any essential oils tends to set off robbing.
>And there is some talk about some sort of menthol affects the trachial mites...
Only the fumes. I've never used menthol at all.