3 foot is kind of pushing it for multiple pairs, IMO
, but you could probably get away with 2 pairs. Don't think I would try 3 pairs but who knows, it could work out if you get lucky. Based on my experience with emperor tetras (lots, lol), I'd leave them out of the list altogether. They grow pretty large for a tetra, are VORACIOUS eaters, and will likely bully the embers. Seriously, when they get size on them they are nippy toward other fish and make it very difficult to get any food to the bottom of the tank (where your dwarf cichlids will all be- they are VERY rarely surface feeders in a tall tank). Embers and cardinals are good choices though.