The Lamarck Angelfish is hardy as well as interesting fish. It exhibits sexual dimorphism, where the males have a bright yellow blotch on the forehead in addition to longer and "sharper" caudal fin edges. Since the Lamarck?s Angelfish features opercular spines, which are used for defense, can lead to severe gill damage if it tangles in net. Therefore, a container with flattened net should be used to cover the top of the container reducing the risk of escape and injury. The juvenile Lamarck?s Angelfish shows very dark body with electric blue markings, but as it matures it will lighten and begin to change its color. Although, it is relatively peaceful with other tank mates, but when it is acclimatized in the tank it becomes territorial. But its aggression can be reduce if are provided with ample swimming space and shelter. The Lamarck?s Angelfish prefers to live in groups of single male and 2-6 females, or a small group of single male and two females in an aquarium of 240+ gallons. The tank should be well-established with live sand substrates and plenty of live rocks for grazing, refuge and territory. Since the Lamarck?s Angelfish is very sensitive to fluctuations in water chemistry, you should use the high quality biological and mechanical filtration along with the high quality protein skimmer.