The Pale-tail Chromis or Yellowtail Blue Damsel displays typical damselfish behavior, very active and a great eater! A good fish for the beginner as it is hardy and inexpensive.
This is a young specimen of the Blue Yellowtail Damselfish, Goldtail Demoiselle or Yellowtail Blue Damsel, about 1 inch long. Generally juveniles like this will be available from a marine fish store. As they mature, their tails loose the yellow and become white and the bright blues become a more bluish grey.
For more Information on keeping this fish see:
Guide to a Happy, Healthy Marine Aquarium
Goldtail Damsel (Chrysiptera parasema)
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Video shows a Goldtail Damsel (Chrysiptera parasema) specimen from the Philippines or Indonesia locations. These have only yellow on the back tail and a little into the body. They are small, mellow for a damsel, and easy to take care of. They do spawn in captivity easily, though rearing the young can be quite difficult.
Beginner Fish: Yellow Tail Blue Damsel
Maintenance: This fish will readily eat all kinds of live, frozen, and flake foods and algae. Finely chopped meaty foods (like brine shrimp) can be fed regularly. It is best to feed small amounts several times a day. In a reef situation they don't really need to be fed very often at all.
Social Behaviors: Like all damselfish, they can be territorial and aggressive, especially as they get older. Can be kept together and with other larger fish but watch them closely to be sure their aggression doesn't become destructive.
Breeding/Reproduction: Some of the damselfish have been bred in captivity. See general breeding techniques under Clownfish on the marine breeding page.
Length/Diameter of fish: Blue Yellowtail Damselfish, Goldtail Demoiselle or Yellowtail Blue Damsel adults can grow to 10 cm ( 4.0 inches) in the wild! Apparently they only get about half that size in captivity.