Thanks for the replies,
These Blueberries are about an inch long and there pincers look like those of a cherry shrimp their same size. My fish where about 0.5 inches. The blueberries are more active than the other shrimp and do bully the other shrimp but do no damage. The top is secure so I am thinking that they may have been sucked up as Somewhatshocked suggested. I have now placed a pre-filter and if all goes well get some boraras urophthalmoides as the stay smaller than other Boraras species.