Yellowtail Blue Damsel

Goldtail Demoiselle, Yellowtail Damselfish

Yellowtail Blue Damselfish, Chrysiptera parasema, Goldtail DemoiselleChrysiptera parasemaPhoto Wiki Commons, Couresty Staszek_Szybki_Jest
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My husband and I are new at the saltwater. After we got our tank set and waited till all was right w/the salt and such, we bought two of these lovely fish. However,... (more)  Diane

The Yellowtail Damselfish is a good fish for the beginner as it is hardy and inexpensive!

The Yellowtail Blue Damselfish Chrysiptera parasema is a beautiful small fish. Its coloring is very dramatic with a bright blue body and a yellow tailfin, but it will only reach about 2 3/4 inches (7 cm) in length. Depending on their location of origin they can also have a yellow pelvic fin and some may have yellow pectoral fins. Another damselfish it can sometimes be confused with is the Azure Damsel Chrysiptera hemcyanea, which is similar in coloring. The Azure also has the yellow fins but is distinguished from the Yellowtail Damselfish because the yellow also extends along the bottom part of the body.

This fish is considered by many aquarists to be the ultimate damselfish. It's an aquarium favorite because it's very active and a great eater. It is also extremely hardy and very is inexpensive to boot. It makes a great choice for beginners, yet is enjoyed by all aquarists. Other common names it is known by are Yellowtail Damselfish, Yellowtail Damsel, and Goldtail Demoiselle.

This is a damsel that will not reign terror in your tank when given plenty of room. They are a great addition to any peaceful community tank, be it a reef or fish only tank. They need a minimum tank size of 20 gallons for one, or a male and female pair if they are the only fish in the tank. Groups can be kept in medium sized tanks of at least 40 gallons, where they will readily get along with other peaceful fish. While they can be kept in a nano tank, they are less likely to cause trouble in larger tanks with other less aggressive tank mates. They are the ones that tend to get picked on by larger, more aggressive fish, so proper tank mates are essential to keep them from being stressed out.

These beautifully marked, smaller damsels are very easy to keep. They are very durable and will readily eat any aquarium food offered. Provide rock work or corals in and around all areas of the tank which offer lots of nooks and crannies for them to hide in. They prefer to hang out at the middle to bottom of the tank. Like all the damsels in the Chrysiptera genus they also like to burrow. They will make areas under rocks to retreat at night, so a sandy bottom is preferred.

For more Information on keeping saltwater fish see:
Marine Aquarium Basics: Guide to a Healthy Saltwater Aquarium

Goldtail Damsel (Chrysiptera parasema)
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Goldtail Demoiselle

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
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Yellowtail Blue Damsel, Chrysiptera parasema

Real nice video showcasing this wonderful beginner saltwater fish. This pretty little fish is also known as the Blue Yellowtail Damselfish and the Goldtail Demoiselle.

Yellowtail Blue Damsel - Quick Aquarium Care
  • Aquarist Experience Level: Beginner
  • Aquarium Hardiness: Very Hardy
  • Minimum Tank Size: 20 gal (76 L)
  • Size of fish - inches: 2.8 inches (6.99 cm)
  • Temperament: Semi-aggressive
  • Temperature: 74.0 to 84.0° F (23.3 to 28.9° C)
  • Range ph: 8.2-8.4
  • Diet Type: Omnivore

Habitat: Distribution / Background

The Yellowtail Blue Damselfish Chrysiptera parasema was described by Fowler in 1918. The genus name was formerly known as Glyphidodontops. This species is also known by the common names Yellowtail Damselfish, Yellowtail Damsel, Goldtail Demoiselle, Yellowtail Demoiselle and Yellowtail Blue Damsel, all of which aptly describe their coloring.

They are found in the Western Pacific, in the Solomon Islands, northern Papua New Guinea, Philippines and Ryukyu Islands. This species is not listed on the IUCN Red List of Threatened Species.

About the Chrysiptera Genus:

This species is a member of the very large Pomacentridae family of Damselfish and Anemonefish. It belongs to the subfamily Pomacentrinae in the large Chrysiptera genus. There are currently 34 recognized species in this genus.

Some Chrysiptera species occur at rather deep reef zones, but the majority are found in the shallower waters of lagoons, sheltered bays, and coastal fringing reefs. They live near coral growth and may hover close to the substrate. They occur singly, in pairs, or in small loose groups. They are omnivores, feeding on plankton, algae, and small benthic crustaceans.

This genus contains some of the most beautiful and brightly colored damselfish, as well as some of the smallest. On average the species range from about 2.8 inches (7 cm) in length to a few centimeters longer. They may be territorial towards conspecifics, but many are not as aggressive as other Pomacentrids towards other types of fish.

Their small size along with the less pugnacious nature of many of the Chrysiptera makes them suitable for the aquarium. Some of the more passive species can even be kept in groups and may get along with more peaceful tankmates. There are exceptions, however, as some species become highly aggressive in the confines of an aquarium as they mature.

About the Yellowtail Blue Damselfish:

The Goldtail Demoiselles prefer densely populated coral groupings in sheltered lagoons and inshore reefs. They are found at depths between 3.3 to 52 feet (1 to 16 m). Small groups, especially juveniles, are found over Acropora colonies.

Adults are typically found by themselves or in pairs, while juveniles are found in small groups. This is one of the more peaceful of the Chrysiptera Genus, yet it is just as sturdy as its conspecifics. It is similar in temperament to a less aggressive clownfish. The Yellowtail Blue Damselfish will swim up to 20” above the substrate to feed on zooplankton, and will also consume other planktonic foods and algae that are near the bottom.

  • Scientific Name: Chrysiptera parasema
  • Social Grouping: Varies - Chrysiptera species occur singly, in pairs, or in small loose groups.
  • IUCN Red List: NE - Not Evaluated or not listed


The Yellowtail Blue Damselfish is a deep bodied fish. These damselfish are small, reaching only up to 2 3/4 inches (7 cm) in length. Similar to other damselfish, their life span in the wild is likely 2 to 6 years and they probably live the typical 15 years in captivity.

This damsels body is an intense medium blue color with a yellow tail fin. Some only have a yellow tail fin, while others may also have the yellow extending onto the body up to the back of the anal and dorsal fin. They can have a yellow pelvic fin as well, and some may have yellow pectoral fins. Although these damsels have a rather distinct look, a couple other fish may be confused with them:

  1. Azure Demoiselle Chrysiptera hemcyanea
    This fish has yellow on the belly, whereas the Yellowtail Damselfish does not.
  2. Blue Devil Damsel Chrysiptera cyanea
    Certain specimens have yellow on the nose and chin, whereas the Yellowtail Damselfish does not. Some Blue Devils have a yellow to orange tail, and their blue is less intense. These fish also grow larger, reaching up to 3.1 inches, and are much more aggressive.

The Yellowtail Blue Damselfish have various quantities of yellow on their tail fins, depending on their location of origination, but yellow is never found on the back or belly. Those that have a yellow tail fin with just a little yellow extending into the body are generally specimens from the Philippines and Indonesia. Specimens from Papua New Guinea may have yellow on their tail fin that extends onto the body to the back of the dorsal and anal fins. Species from this area may have yellow pectoral and/or pelvic fins as well.

  • Size of fish - inches: 2.8 inches (6.99 cm)
  • Lifespan: 15 years - Damselfish generally live up to 6 years in the wild and up to 15 years in captivity.

Fish Keeping Difficulty

The Yellowtail Blue Damselfish are durable and very easy to care for. They make a great addition for the beginning saltwater hobbyist or any other marine aquarist. These attractive “Demoiselles” are hardy little fish and great eaters. They will help with algae control and appreciate meaty foods as well. They tolerate a wide range of non-fluctuating temperatures, but even though they are quite durable, they can still fall ill if exposed to poor water conditions for too long.

The tank needs to be at least 20 gallons for one damsel or for a mated pair, so make sure water changes are frequent in such small tanks. They will be quite happy in a reef or a fish only community tank, but as they are often preyed upon in nature, they need peaceful companions and a lot of places to hide in rock work or corals to feel safe. Doing normal water changes, feeding them a variety of foods several times a day, and having proper tank mates will keep this damselfish happy and healthy.

  • Aquarium Hardiness: Very Hardy
  • Aquarist Experience Level: Beginner - They are suitable for the beginner, but being a more peaceful damselfish, tankmates must be selected with care.

Foods and Feeding

The Yellowtail Blue Damselfish are omnivores. In the wild they feed on zooplankton, and will also consume other planktonic foods and algae. In the aquarium provide variety in their diet that includes plenty of proteins as well as some vegetable foods.

Offer meaty foods like mysis shrimp, vitamin-enriched brine shrimp, cyclops, finely shredded frozen seafoods, and preparations for omnivores. These foods can be given as freeze dried, frozen, sinking pellets, flake or fresh. You can also offer some flakes and other preparations for herbivores. Color enhancing foods can help maintain their bright coloring.

It is best to feed small amounts of food several times a day. Feeding them more often helps to dissipate any possible aggression within a tank, since food is the biggest reason for protecting their little patch of the reef or tank. Sinking pellets work great because these fish tend to feed near the bottom of the tank. If feeding pellets, make sure they are wet before adding them to the tank so air will not enter into their digestive tract, which can cause issues.

  • Diet Type: Omnivore
  • Flake Food: Yes
  • Tablet / Pellet: Yes - Make sure to soak pellets for a few seconds to dispel any air. Use sinking pellets since they stick close to the bottom, and preferably those designed for carnivores.
  • Live foods (fishes, shrimps, worms): Some of Diet - Only needed if you want to offer a treat or condition them to spawn.
  • Vegetable Food: Some of Diet
  • Meaty Food: Most of Diet
  • Feeding Frequency: Several feedings per day - Feed several times a day, this also helps to counter any possible aggression.

Aquarium Care

These damselfish are hardy and easy to keep with a well maintained tank. Minimum tank size is 20 gallons, so make sure water changes are frequent in such a small tank. Regular water changes performed bi-weekly will help replace the trace elements that the fish and corals use up. Guidelines for water changes with different types and sizes of aquariums are:

  • Fish only tanks:
    • Nano/Small tanks up to 40 gallons, perform 5% water changes bi-weekly.
    • Medium sized tanks up to 90 gallons, perform 15% bi-weekly.
    • Large tanks 100 gallons and over, once water is aged and stable, can be changed 10% bi-weekly to 20% monthly, depending on bioload.
  • Reef tanks:
    • Nano/Small tanks up to 40 gallons, perform 15% water changes bi-weekly.
    • Medium sized tanks up to 90 gallons, perform 20% to 30% monthly depending on bioload.
    • Large tanks 100 gallons and over, once water is aged and stable, can be changed 20% to 30% every 6 weeks depending on bioload.

For more information on maintaining a saltwater aquarium see: Saltwater Aquarium Basics: Maintenance. A reef tank will require specialized filtration and lighting equipment. Learn more about reef keeping see: Mini Reef Aquarium Basics.

  • Water Changes: Bi-weekly - Do bi-weekly water changes of 15% in a reef setting or 20% monthly in a fish only tank.

Aquarium Setup

The Yellowtail Blue Damselfish can be happily kept in a reef setting as well as in a fish only peaceful community tank. They typically only grow to 2 3/4 inches, so the minimum tank size is 20 gallons for one, or for a mated pair. In that small size of an aquarium, however, be very careful when adding other fish since they are territorial, especially if you have a mated pair. They can also be kept in a nano tank if they are the only fish in the tank.

A larger tank will be needed to keep them with other fish. Housing them in tanks over 40 gallons will allow plenty of territory for them to occupy and they shouldn’t bother the other peaceful fish you want to add. If keeping other peaceful damsels, including less aggressive clownfish, add them at a rate of 1 fish per 15 gallons. If you are going to have larger fish like a large surgeonfish/tangs, the tank size should fit the larger fish’s needs.

These are one of the less aggressive damselfish. They swim in mid to lower areas of the tank, but as they are often preyed upon in nature, they need many places to hide to feel secure. They will appreciate little crevices, nooks and crannies created within rock work (preferably live rock), corals, or other decor. They appreciate branching stony corals to retreat into, be it live or artificial, which helps simulate their natural environment. In the wild, the Chrysiptera genus are found in areas of rubble, and like to dig their nests underneath dead corals, a 1/2 clam shell, or rubble. A substrate of sand will make it easier for them to burrow in. You can also add a larger shell for them to lay their eggs in.

There are no special requirements for water movement or lighting, unless housed with corals, in which case the coral requirements will need to be considered. Water temperatures between 74°F to 84°F (23° - 29°C), with pH from 8.2 to 8.4 will keep them happy and healthy. Breeding temperature should be similar to clownfish, with optimal spawning production occurring between 79°F to 83°F (26°C to 28°C).

  • Minimum Tank Size: 20 gal (76 L) - A 20 gallon tank is suggested for one fish or a male and female. A larger tank, of 40 gallons or more is suggest when keeping with other peaceful fish.
  • Suitable for Nano Tank: Yes - This fish should be alone or as a mated pair in this size tank.
  • Live Rock Requirement: Typical Plus Hiding Places - Provide places for them to hide within rockwork or coral.
  • Substrate Type: Sand - Chrysiptera species like to burrow under rubble, coral (they will not harm the coral), and dead coral.
  • Lighting Needs: Any - It has no special lighting requirements, though if kept with live coral the coral may need strong lighting.
  • Temperature: 74.0 to 84.0° F (23.3 to 28.9° C)
  • Breeding Temperature: 79.0° F - The optimal temperature for good quality eggs and larvae occurs with temperatures of 79° F to 82° F (26° - 28°C).
  • Specific gravity: 1.023-1.025 SG
  • Range ph: 8.2-8.4
  • Brackish: No
  • Water Movement: Any
  • Water Region: Bottom - hey inhabit the mid to lower areas of the tank.

Social Behaviors

This genus of damsels, the Chrysiptera, has a wide array of temperaments with the Yellowtail Blue Damselfish being one of the less aggressive. Like all damsels, however, they can become territorial and aggressive when kept as a pair and as they get older. Still they are not anywhere near as aggressive as their cousin the Blue Devil Damsel Chrysiptera cyanea!

These are one of the less aggressive of the damselfish, with a temperament that is closer to a less aggressive clownfish. The minimum tank size is 20 gallons when kept alone or as a mated pair. .You may keep them in small groups by “crowding” with other peaceful damselfish at a rate of 1 fish per 15 gallons. With a spawning pair the male will viciously guard his eggs, at which point, a separate tank may be needed if he starts attacking tank mates. Larger tanks of at least 60 gallons should make this situation less volatile.

They will get along with peaceful, passive fish in these larger tanks though you should allow the peaceful tank mates to become established first. They do not seem to be bothered by most other peaceful and semi-aggressive fish, except the more aggressive damsels or clownfish such as the Clarkii clownfish Amphiprion clarkii. Only adding other damsels that are peaceful is suggested and if adding a clownfish, try the more peaceful peaceful Percula Clownfish Amphiprion percula, Ocellaris Clownfish Amphiprion ocellaris, or Pink Skunk Clownfish Amphiprion perideraion. Tanks over 55-60 gallons should allow both to get along without any trouble, as long as their territories are at least two feet apart.

Keep an eye on semi-aggressive fish to be sure they are not harassing your Yellowtail Blue Damselfish. Very aggressive dwarf or pygmy angelfish and very aggressive roaming clownfish may attack the this damsel. Do not house them with larger semi-aggressive fish who are also planktivores, like anthias, or any sized aggressive fish. They will not do well with aggressive fish at all, and tend to be the ones picked on by fish that are larger and more aggressive than they are. Predatory fish are also out of the question, since they may eventually eat your damsel!

In a reef setting the Yellowtail Blue Damselfish thrive. They make a great addition to a reef because they pose no threat to corals. In fact branching stony corals benefit from the flutter of their fins between their branches, helping to dislodge detritus. Bottlebrush Acropora seem to be a favored coral. They will also happily pick off any algae growing at the base of a hard coral. They won't bother any large or small invertebrates, though they may eat a copepod or two.

  • Venomous: No
  • Temperament: Semi-aggressive - Although they are considered semi-aggressive, they are one of the less aggressive of their genus.
  • Compatible with:
    • Same species - conspecifics: Yes - Adults can be kept singly or housed as a male/female pair, and as juveniles in small groups.
    • Peaceful fish (gobies, dartfish, assessors, fairy wrasses): Safe - Safe in tanks of 40 gallons or more.
    • Semi-Aggressive (anthias, clownfish, dwarf angels): Monitor - Only safe in tanks of 55 gallons or more. Avoid very aggressive clowns such as clarks and aggressive anthias unless tank is at least 100 gallons.
    • Semi-Aggressive (anthias, clownfish, dwarf angels): Monitor - Only safe in tanks of 55 gallons or more. Avoid very aggressive clowns such as clarks and aggressive anthias unless tank is at least 100 gallons.
    • Aggressive (dottybacks, 6-line & 8-line wrasse, damselfish): Monitor - Dottybacks will be too aggressive. Other small damsels with a similar mild temperament can be kept if the tank is at least 60 gallons. Six- and Eight-line Wrasses may harass your Talbot’s in smaller tanks.
    • Large Semi-Aggressive (tangs, large angels, large wrasses): Monitor - These damsels may picked on by aggressive large angelfish. Add first and provide multiple hiding places and allow them to acclimate before adding this type of fish.
    • Large Aggressive, Predatory (lionfish, groupers, soapfish): Threat - Do not house with fish large enough to swallow them. Even a smaller predatory fish that cannot swallow them whole would make these damselfish too afraid to come out and feed.
    • Slow Swimmers & Eaters (seahorses, pipefish, mandarins): Monitor - These damsels will out compete them for food in smaller tanks. Larger tanks over 100 gallons should provide enough food for all. 

    • Anemones: Safe
    • Mushroom Anemones - Corallimorphs: Safe
    • LPS corals: Safe
    • SPS corals: Safe - Actually beneficial as the presence of the Yellowtail Blue Damselfish helps to dislodge
    • Gorgonians, Sea Fans: Safe
    • Leather Corals: Safe
    • Soft Corals (xenias, tree corals): Safe
    • Star Polyps, Organ Pipe Coral: Safe
    • Zoanthids - Button Polyps, Sea Mats: Safe
    • Sponges, Tunicates: Safe
    • Shrimps, Crabs, Snails: Safe
    • Starfish: Safe
    • Feather Dusters, Bristle Worms, Flatworms: Safe
    • Clams, Scallops, Oysters: Safe
    • Copepods, Amphipods, Mini Brittle Stars: Safe - May eat some copepods but should not decimate populations.

Sex: Sexual differences

Sexual differences are unknown, though males may be larger.

Breeding / Reproduction

All damsel species are similar to clownfish and follow the general breeding pattern of clownfish. Successful breeding requires perfect water parameters and a large, non-predatory aquarium system. If breeding in captivity, note that brittle stars, serpent stars, wrasses and crabs will eat the eggs of damselfish. The eggs and larvae are much smaller than clownfish, and are difficult to rear.

The Yellowtail Blue Damselfish readily spawns in captivity. They need the water temperature to be between 79°F to 83°F (26°C to 28°C). Similar to others in their genus, in the wild, males have their own territory, which is near a nesting site.This site has rubble or a half of a shell from a clam as the roof and a burrow underneath. The day before the spawning ritual begins, a female will visit the males in her colony. When she chooses a fit and healthy partner she will stop swimming, and facing upward, will flash a light ring around each eye.

After she sends the signal the male whose nest she wants to inspect responds by acting out displays. These displays are also evaluated! The female will then follow the male to his nest after his display to see how many eggs he has. She will stay up to 20 minutes inspecting his “crib” and then move on to the next male. She is not ready to lay her eggs during this evaluation and she is very picky. She will review many of the potential mates, even traveling up to 325 feet (100 m) in distance from nest site to nest site.

At dawn of the next day, the female will then spawn with the male that she decided would be the best candidate. This male that is chosen is typically the largest and the male with the most eggs. If there is another female at the nest who wants to spawn with the same male, she will wait her turn at the entrance of the nest. Up to 4 females have been seen at one nest site spawning one at a time, one after the other, with the same male.

These nests can have almost 10,000 eggs from several different females! Males have been known to abandon their small eggs clutch to take over  larger abandoned egg clutches of another male. They know that the more eggs they have in their nest, the better the chance the female will spawn with them. The male will stay and protect his eggs until they have hatched, which can take up 4 days in the wild, depending on water temperature. The larval stage for Chrysiptera species can last between 10 to 50 days.

The Yellowtail Blue Damselfish have been known to spawn easily in captivity, with the one female depositing around 300 eggs. The eggs will hatch within 96 hours when the temperature is 84˚F (28˚C). They hatch a couple of hours after the lights are turned off. Once they are are all hatched, Olivotto, 2003, suggests feeding the larvae PUFA as their first food and keeping the light on 24 hours a day for the larvae to survive. This produces “green water” which helps to maintain better water quality due to the decreasing of waste by the larvae. Water changes of 10-30% per day, cleaning the bottom of the bare tank is essential. See general breeding techniques under Clownfish on the Marine Fish Breeding page.

  • Ease of Breeding: Moderate - The eggs and larvae of damselfish are quite small and the fry are difficult to rear.

Fish Diseases

Demoiselles of the Chrysiptera genus are very durable damsels once acclimated. The most dangerous time in their lives is the shipping stress they deal with. Overall they are tough and do not often fall ill, but it has been documented that there seems to be an unexplained “sudden death” that damselfish can fall victim to. There are no signs, the fish is just dead one day. They can contract any normal disease that other saltwater fish are susceptible to. But it is pretty rare unless they are captured with an illness already in motion, so a quarantine period is a good idea.

Damselfish are susceptible to Marine Ich Cryptocaryon irritans, also called White Spot Disease or Crypt, Marine Velvet or Velvet Disease Oodinium ocellatum (Syns: Amyloodinium ocellatum, Branchiophilus maris), and Uronema disease Uronema marinum. All of these are parasites.

The most easily cured of these is Crypt (salt water Ich), but they are all treatable if caught in a timely manner. Marine Velvet is a parasitic skin flagellate and one of the most common maladies experienced in the marine aquarium. It is fast moving and primarily infects the gills. Uronema disease, which is typically a secondary infection, is very deadly and will attack your damsel quickly and lethally.The first symptom is lack of appetite. It is most often contracted when the aquarist lowers the salinity to treat another type of illness, but doesn't lower it far enough. This parasite thrives in mid-level brackish water salinity, which is a specific gravity of around 1.013 to 1.020.

Treat your new damselfish as gingerly as you would any other saltwater fish, and they will respond well. Anything you add to your tank that has not been properly cleaned or quarantined, including live rock, corals and fish can introduce disease. The best prevention is to properly clean or quarantine anything you want to add to the tank. For information about saltwater fish diseases and illnesses, see Aquarium Fish Diseases and Treatments.


The Yellowtail Blue Damselfish are readily available and are inexpensive. They can obtain from stores and online


Author: Clarice Brough CFS, Carrie McBirney, David Brough CFS
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Lastest Animal Stories on Yellowtail Blue Damsel

Diane - 2009-10-29
My husband and I are new at the saltwater. After we got our tank set and waited till all was right w/the salt and such, we bought two of these lovely fish. However, after we put them in, we can't seem to find them anymore, we are confused as there are no other fish in the tank. Hope to see them soon.

  • carly - 2010-09-19
    Um the last time I had one of these fish it jumped right out of the tank and we found it dried out on the floor =( but they could just be hiding too.
  • Bill - 2012-07-24
    If they are small and you have an over flow on your thank they might have fallen into the overflow so you might have to fish them out if they are still alive. If the tank is new and rocks were not set up sturdy enough a rock might have fallen on one of them. Both of these have happened to me. My experience with damsels is that they usually don't hide. Especially if they are the only fish in the tank! Most of them are fearless. Every time I have ever gotten more than one damsel, they have killed their conspecifics until there was only one left. But those are the blue devil damsels. If one is chasing the other it would be possible that one just jumps out of the tank too, so I would look around the tank also
  • Jeremy Roche - 2012-07-25
    May have jump, got sucked into filter, check sump.  Maybe try sifting the sand a bit.
Ryan - 2009-06-29
Damsels are good fish for the cycle process and are cute while they are young or juvenile. When they age, like people, they lose their vibrance and become a little more cranky. I house 2 of them now, a yellowtail and a velvet in a 55 gallon reef tank. I was going to trade or sell the damsels after the cycle process was completed but I noticed them eating algae off the rocks in between the zoas and the paly's that the turbo snails can't get at so I am thinking now that I may keep them around. Typically they hate anything new in their space but mine seem oddly docile...they don't attack other fish, even new tank mates. They do go after the snails and my hermit crabs but I can't tell if it is an aggressive lunge or if they are eating off the shells. It appears as though they are just picking stuff off the shells.
Conserve the reefs..propagate your corals.

Kate - 2009-02-18
I've had my yellow tail damsel for almost a year now, it was the first fish in my tank. I've had fish come and go in my tank due to various reasons, but my yellow tail has held on thick and thin and is by far the hardiest fish I've ever had. However, he is aggressive with new fish, though only shortly after he "tells them he's boss". My damsel is cautious and loves swimming in and out of my rock. He is getting "lighter" in color as he gets older. This is a great fish starting out and isn't that aggressive.

Julija Belogubova - 2011-12-12
About a week ago we added the cute yellow tail blues damsels to our existing collection of a yellow tang, skeleton gobie, star fish and a boxing shrimp.
All was well until a couple of days ago when one of the damsels was picked on by the other two. This lead to stress and even with isolation eventually death. But .... this is not all, now the other two have been swimming on there sides (flirting with each other)????? as we see it. Also they seem to change colour of their beards to a light grey?!?!? This only lasts for the same time as the flirting is going on..

Can anyone help but shedding light onto this?