What about Electric Blue Cichlids. As long as the Labs are the same size there should be no prob.The Electric Blues grow to about 20cn and are carnivorious.
Temperament: Extremely territorial and very aggressive.
Comments: Zebras come in an assortment of colors and are an attractive addition to aquariums. They are a good beginner fish as they are hardy but must be cautioned for their temperament. They will prove to be one of the most intelligent of the fresh water species.
you'll need lots of rocks/territoriess to house these guy's w/the yellow labs and i wouldn't add less than 3,that's just my opinion/experience.