I was looking on Alfs site as well in the krobia section and these might be a match
Krobia potaroensis?
http/www.lem.net/alf/css-krobia.htm
well worth contacting as Matt said he is a really help full guy.
I think if they were labeled as Krobia there is a decent chance they are some kind of Krobia but with the group being so un deffined they might even be some kind of local variant that has just been labeled up as that. You do get these kind of contaminations and MAs are actually quite good - as in some of the best stores in the country to have rare fish in so its not hard to believe that an eagle eyed staff member saw the unusual name - or thought that all Krobia were the xingu orange ones and ordered them in.
A bit of a hap-hazard theory but stranger things happen in the hobby - like finding a farm shop, with an aquatics center in the middle of East Yorkshire in the middle of no where that had a pool of huge clown knifes lool - that was my weekend anyway
having seem the aequidens tetramerus i remeber them having a distinct white outline on the tail spot. if you are thinking aequidens againthem email a pic and message to Alf and he will tell you
Well i just got an email back from alf strasberg and he is sure its not a krobia, he believes its some sort of Cichlasoma. So after checking on google im thinking they are possibly Cichlasoma boliviense. What are your thoughts?