I would recomend a 10 gallon, but I suppose you could pull off a 6.6gal. The problem with bamboo shrimp is that you need strong water circulation because bamboo shrimp have fan like arms which catches dbris and micro organism in which these shrimp feed off of.
The 6.6 gallon tank is a bookshelf tank that I would like to put on my desk when I buy it. It has a filter that would provide circulation and if it wasn't enough I would add a powerhead or additional filter, air pump. I can turn a tank into a whirlpool if I thought it was necessary. I was thinking of putting Neon Tetras or cardinals and the shrimp in it.