The Mertensii Butterflyfish, also known as the Orangetail Butterflyfish, or Crowned Pearlyscale Butterflyfish, is a blue silver coloration with black margins on its body scales. This gives a criss-cross pattern and pearly sheen. Most of its posterior is orange and it has a silver-edged black stripe through the eye. It may reside in a 120 gallon or larger aquarium provided that it is well-maintained and relatively peaceful. It may be kept with other Butterflyfish if they are introduced to the tank at the same time. The Mertensii Butterfly is not considered reef safe.