The majority of the roughly 33,400 fish species currently known to science have never yet been maintained in the aquarium. Little more is known of them than that they exist. And even that often isn’t certain, as in the course of the centuries – as is well known, our modern zoology started in 1758 with the 10th edition of Carl von Linné’s book Systema naturae (= The System of Nature) and Linné still believed in the original creation by God and the immutability of species – our view as to what actually constitutes a species has undergone frequent and fundamental changes.