It seems most likely that this strange kissing ritual has actually evolved as a way of settling disputes, without the fish having resorting to more aggressive behaviour, rather than as a sign of affection. It could be a trial of strength. Kissing gouramis (Helostoma temminckii) will anchor their fleshy lips together, until one breaks the contact.

You cannot sex these fish visually outside the breeding period - only when the female then swells with eggs can they be distinguished. There are two colours in existence - the natural grey form, and the more commonly-kept rose-pink domesticated variety. These do not reflect a difference in gender.