Hello,
there is very little in US Aquarium literature in the 1960s and 1970s about the Parosphromenus species (prior to this I have not been able to find any reference to Parosphromenus species; it is possible they did not show up in the aquarium hobby since they tend to travel poorly if not given the right care and conditions). Most of the earliest photographs of these fish arrived in the US from European aquarists who received these fish and those who were successful in spawning them. The book by Vierke in the 1980s was perhaps the first that showed the beauty of this fishes, particularly during spawning.