Did you know fantastic help is an anagram of Planet Catfish? This forum is for those of you with pictures of your catfish who are looking for help identifying them. There are many here to help and a firm ID is the first step towards keeping your catfish in the best conditions.
Definitely a Scleromystax, probably barbatus. I would suggest the only way to know they are kronei is if you know the origin of the fish, either which part of Brazil or who was the breeder. Adults of the two species are very similar and juvenilles are impossible to tell apart.
I see from your fish list you have macropterus. A very rarely available Scleromystax. Are there breeders in the U.S or are these wild caught in orgin? I think we all know they are banned from export but they do crop up from time to time.
Mark Walters Editor of Catchat - The Journal of the Catfish Study Group