I see three Crabro: 1 Male and 2 Females.
Look at the fourth, fifth, and sixth pictures (they stay relatively static through these three photos) - the first female is in the middle of the left half above an Acei and to the right of another Acei. The other female is in the right half halfway up and behind the column of bubbles. The male, located in the middle of the right half above a very nicely colored Lab and to the right of the second female, is hardly distinguishable from the background.
I think they make a nice addition to the tank. Something different than the rest of the fish. The male looks very nice (from what you can discern).