Assortment - particular species of fishes are classed to categories in accordance to aquaristic point of view
System - particular species of fishes are classed to sort and family in accordance to zoological point of view
Occurence - particular species of fishes are classed to groups in accordance to their occurence, respectively in line with continents and particular areas. This is only an aproximate classification, and it does not need to correspond to reality at all. Detailed informations about occurence of particular species are sometimes very hardly searchable. The basic informative source is Fishbase. So we please for forbearance, we try to prepare at least aproximate possibility of choosing of fishes accordingly to their occurence.
The main informative sources for terminology, classification to system and other informations about particular species are Fishbase, Aquatab, Planetcatfish.