We weren’t sure if these tetras would be considered stacked and thought to ask the CD.com community. This may be really clear cut and we totally missed it, but maybe it’s not. I don’t know, really.
See attached photo. Look closely.
http://www.chiefdelphi.com/forums/showthread.php?t=32822&highlight=tetra+blue+red+stack
I believe this thread answers this question.
So, based on this discussion, it seems that they’re considered as stacked. Good to know.