Actually, that is only partially correct. S. marginatus normally has "V" at the base that extends out. This later fills in (sort of like a cup of coffee) to the edge or near edge of the tail depending on age. Both S. sanchezi and the compressus group are an odd bunch when it comes to the tail. It can have both a bold black edge or faint black edge. I think much of it is due to stress (faint colors) and/or water conditions. The single fish in view is S. sanchezi. I didn't comment on the rest because I would need to manipulate the photo to put the fishes upright and I don't have much time to mess with it.jerry_plakyda Posted Today, 08:21 AM
My personal feeling is compressus due to the caudal fin. Marginatus would have a hyaline edge.