The Spot Tail Dartfish, Ptereleotris heteroptera, is entirely blue with one black spot on the tail. They are very peaceful and can be housed with other peaceful fish in a reef tank setting, but may become territorial towards other blennies, gobies or dartfish in smaller tanks.
Dartfish tend to stay mainly towards the bottom of the tank, burrowing and sifting through the sand. However, they are also known for jumping, so a tight fitting lid is suggested. Diet should include a variety of frozen or live mysis shrimp and vitamin enriched brine shrimp 1-2 times daily.