ok, I figured it out... looking at my south American tetra tank, there is an angel fish in that tank, and a spotted silver dollar as a companion fish... the dollar was at the back of the tank facing me, and blended into the tank background... here it is, angled away slightly, so you can make it out... for a couple minutes it was completely lined up perfectly, and i couldn't make it out as a fish... these thin, wide sided fish, can be very hard to see, if they are facing you, rather than sideways...
