Damselfish can add depth to your marine tank like no other saltwater fish. They are relatively low-maintenance and have an explosive temperament that could be their undoing if you’re not vigilant!
They are relatively widespread among hobbyists due to their robust immune systems (they won’t die easy) and hold their own against large species but will go after fish that encroach on their territory.
It is important to note that there are several Damselfish variants, and we will try to cover some species here, but the goal would be to cover the most popular variant – the Blue Damselfish. These are among the most popular saltwater fish because of their durability and appearance.
Species Overview
| Level of Care | Very Easy |
| Temperament | Aggressive |
| Appearance | Various colors |
| Life Expectancy | 6 years or more |
| Size | Reach a size of 3 inches up to a maximum of 12 inches for certain species |
| Diet | Omnivorous with meat-eating tendencies |
| Family | Pomacentridae |
| Tank Size | 30 gallons |
| Tank Environment | Marine tank |
| Tank Mates | Must be careful choosing tank mates |
With a temper that runs boiling 99% of the time, the damselfish have earned a very apt nickname, “the Blue Devil.” They’re bright blue and always angry, ready to engage fish that are massive in size despite being just a few inches tall.
They originate in tropical coral reefs but can be found in temperate climates as well. One prominent hotspot is near the Catalina Islands in California.
A few damselfish variants have been found in freshwater lagoons, brackish waters, and even mangroves. Some variants have been spotted in warm climates of the Pacific Mexican coast, like the Garibaldi fish.
The main draw of damselfish, apart from their striking appearance, is that they are incredibly hardy. Fish do not require a specialized diet and will do just fine with any food you feed them.
In the older days of fishkeeping, before fishless cycling became commonplace, damselfish would be used to cycle saltwater tanks because they could tolerate levels of nitrates, nitrites, and ammonia that could otherwise kill off any other saltwater fish.
Most variants live within water columns, but some have been found to live at a depth of up to 100 meters.
Appearance
Most Damsel fish variants have different appearances, but their primary structure and color are nearly the same. They feature a deep-colored body, a forked tail very similar to Cichlids, and feature two nostrils on either side of their head, along with two anal spines.
They can be found in vibrant shades, including blue, yellow, orange, and red.
Size
The average Damselfish size is only about 3 inches in length, but some of the rarer variants have been known to reach 14” in size as well.
Behavior & Temperament
Yes. Most damselfish are known for being violent towards other fish, especially species that don’t know how to defend themselves.
Their temper has earned them a pretty bad rep in the fishkeeping hobby. They’re so aggressive that they’ll try to bite your hand if you put it in the tank.
Blue damselfish have been known to continually harass their less aggressive and docile tank mates, sometimes to the point of death. Even though most of them are small in size, they are very territorial and will try to claim the whole tank if it is small.
Anything they deem to be their spot, they will aggressively defend. They will chase and nip at other fish around that don’t fight back. It requires keeping a very close eye on them to spot aggressive behavior. Fish that are victims of such behavior will become stressed and withdraw, causing them to become sick and stop eating.
When they aren’t harassing other fish or defending their territory, the Blue Damselfish will spend much of its time feeding. Small variants will swim to the bottom of the water column, while large ones prefer to feed higher.
Different Types of Damselfish
Blue Damselfish
They grow to over 3 inches in length and are bright blue in appearance. Males have a yellow-colored tail with a snout, but females and juveniles lack these yellow highlights. You’ll notice that when Blue Damselfish feel threatened, they turn black in just a matter of seconds. It is a great way to tell if they’re stressed out.
Bicolor Damselfish
These fish are native to the Caribbean oceans and carry the scientific name, Stegastes partitions. The front half of their body is dark black/grey, and the rear is pale. They are pretty big at about 4 inches and, therefore, a little more aggressive than the Blue Damselfish.
Yellowtail Damselfish
These popular damselfish have a blue body, like the Blue Damselfish, but they have a prominent yellow tail fin. They reach only 3 inches in size and are often regarded as among the best types of damselfish because they’re not very aggressive.
Four Stripe Damselfish
They have four alternate black and white bands, because of that, they’ve got the name Four Stripe Damselfish. The last black band can be seen on the tail. They can reach 4” in size, are semi-aggressive and hardy.
Azure Damselfish
They are also known as the Half-Blue Damsel fish because their body is parts blue and parts yellow. They only grow to about 3 inches and are tough.
Domino Damselfish
Domino damselfish, also known as the Dascyllus trimaculatus, is named because of the three distinct white spots on their body. They can grow to a length of 5 inches in size, which is pretty big as far as damselfish go, and therefore, too aggressive to other species.
Food & Diet
They are omnivorous and prefer to eat both live and frozen food, especially flake foods. Some Damselfish species are herbivorous and prefer a diet of vegetables, so do your research before selecting the right food for your fish. The Blue Damselfish is omnivorous but enjoys eating lots of protein-rich foods, including copepods, shrimp, squid, and small meat pieces.
In the wild, damselfish have a varied diet that comprises plankton, algae, small crustaceans, and small yolky eggs that belong to other fish.
Tank Mates
They are very aggressive towards other fish, including their kind. It is not recommended to keep different species of Damsels together in the same tank as a general rule.
You should stick to just one species of damselfish per tank. If the tank is tiny, do not mix two or more different species – this is a recipe for disaster.
You can introduce other fish only if you’ve got a relatively large tank. Ideal tank mates include similarly sized fish that are semi-aggressive and know how to fight back. Avoid timid species altogether.
It is recommended to introduce them into the aquarium last. This way, every other species will have claimed their territory and prevent the damselfish from going on a quest to liberate different tank areas.
Oddly enough, damselfish get along fine with most invertebrates, but if they’re too small, they may get mistaken for food from time to time. If you were to ask us, we’d avoid adding invertebrates altogether as well because they’re just too vulnerable.
Below is our list of the best saltwater tank mates for damselfish:
Clownfish and damselfish share nearly the same water requirements and will peacefully co-exist together.
However, you will need to provide them with a large enough tank, at least 30 gallons; otherwise, there would be too much in-fighting.
Ideal Tank Conditions
You need to check the type of water that you plan on introducing in your Damsel fish tank. Most Damselfish variants are saltwater species, which means you need to use marine water in the Aquarium. You can either buy marine water online or from a pet store. You could also prepare some saltwater at home by de-ionizing water with sea salt mix.
Do not mix table salt with the water instead of sea salt because that will jeopardize their health. If your damselfish happens to live in brackish or freshwater, you can provide fish with tap water as well.
Most damselfish are small in size and only reach an average of 3 inches of length. The average tank size should be about 30 gallons, but if you’re planning on keeping more than one, consider upgrading to about 50 gallons or more. If you want to keep a school of 4 Damselfish or more, you will need a 100-gallon tank.
If your Damsel fish grows a bit too long in size, for instance, 12 inches, you will need at least a 100-gallon tank. While it’s true that damselfish are very hardy, they will die in smaller tanks.
Because they are so incredibly versatile, these can adapt to a wide range of water conditions. However, it would help if you strived to mimic their natural habitat in your saltwater tank.
The water temperature should be kept at around 74 to 80° Fahrenheit, with pH values of between 8.1 to 8.4 and a specific gravity of 1.022 to 1.025. Should keep the water’s carbonate hardness at around 9° to 12°.
It is recommended to install an aquarium heater to regulate the temperature at the desired amount. Use a thermometer to monitor the temperature to ensure your damselfish is enjoying its new home. Conduct a pH test every week with a litmus paper or some other pH testing kits.
Tank Setup
Damselfish need to have their cave, or they will not do well in your tank. These fish have been known to charge drivers who swim too near to their rocky homes in the wild.
It would help if you chose soft sand, not hard gravel, for the substrate because it could harm their fragile bodies. Just make sure to include lots of rocks, caves, and plants to provide ample cover for your damselfish and places to explore. It also keeps their aggressive nature in check.
When choosing the plants for your damselfish, it is essential to choose a combination that will fit all the tank inhabitants. Will the plant be too aggressive toward them? Will they accept the plant? The most important thing is to ensure that all the plants you choose are healthy and adequately quarantined for a few weeks before introducing them into the tank.
Sick plants will have bacteria that will aggressively attack other plants and release chemicals into the water that could upset the tank’s entire balance. So be careful! Below are a few saltwater plants that you may want to introduce in a tank full of damselfish:
Turtle Grass Shoots
Turtle Grass shoots are fun to watch and an excellent spot for small fish and invertebrates alike to hang around. Your damselfish may also swim to the broad leaves in search of some cover. It needs a sandy substrate that is about 6 inches deep enough to help it spread its roots.
Mermaid’s Fan
This tropical plant originates in the Caribbean ocean. It can be planted in both substrates and live rock. Most damselfish do not feed on them, so they’re an excellent fit for most aquariums. These plants need calcium to grow and don’t tolerate high levels of nitrate and phosphates. If they’re not doing too well in an aquarium, it’s a sign that other fish aren’t doing too well either.
Tufted Joint Algae
This small, segmented green plant has small tufts near the end of each branch that looks incredibly fun to watch. Tufted joint algae oxygenate the water and are known for controlling nitrogen levels. They require some water flow to thrive and must be anchored to a reef for survival.
Blue Hypnea Algae
They’re unique because of their unique iridescent blue color that adds a lot of flair to any tank. This plant can absorb phosphates and nitrates in a tank, making it ideal for small marine inhabitants.
Shaving Blue Plant
Those long leaves bear an uncanny resemblance to pipe cleaners. The ‘shaving’ blue plant is pretty good at regulating nutrient levels in a tank, particularly phosphates and nitrates. It does need some light exposure or good results. These plants require iron supplementation to survive.
Breeding Guidelines
Unlike most saltwater species that lay their eggs on the water surface, damselfish lay their eggs on the substrate. Male will try to court females by various means.
He will change his body’s color, emit clicking sounds, and make random voracious movements in the tank. If the female accepts his little dance routine, the male will initiate the spawning session.
The female will lay her eggs on the male’s preferred nesting site and aggressively defend it from other fish. Males may exhibit a violent behavior known as filial cannibalism.
They eat some of their eggs to gain the necessary energy needed to care for well-developed eggs. Their parental nature is to eat dead eggs to prevent the spread of a fungus that could affect other eggs’ health.
Eggs will take around four days to a week to hatch. Juveniles eat zooplankton and phytoplankton to sustain themselves. They take a long time to reach maturity, about 2 to 3 years, or even longer, depending on the variant in question.
It is worth noting that breeding Damselfish in captivity is easier said than done. Most aquarists don’t have the patience to wait for a pair to mate and prefer to buy new one. Nevertheless, you can still keep pairs together and wait for them to mate.
Common Diseases and Dangers
The primary reason why most damselfish die early is due to prolonged exposure to unhealthy levels of ammonia. Due to this, their bodies turn a dark color and spots, and they eventually die.
It is not a good idea to introduce them as the first inhabitant of the Aquarium to create a nitrogen cycle. Not only is this strictly prohibited, but it is also unethical because creating a nitrogen cycle puts a tremendous strain on their body. Live rocks will do just the same for you.
Other than that, Blue Damselfish are vulnerable to specific parasitic diseases such as the following:
- Marine Ich
- Marine Velvet Disease
- Treponema Disease
If you suspect your fish is under the weather, consult your vet as soon as possible. Most hobbyists advise keeping the water’s salinity at around 1.010 to ward off parasites, but this will also affect your damselfish health.
Where to Buy?
Because they are such a popular saltwater fish, Blue Damselfish – and indeed, most variants of damselfish – are easy to purchase from typical marine pet stores, online stores, and online forums. Rare species may be hard to come by and will cost a fortune.
Final Thoughts
If you are looking to add a hat blue, bright splash os f color to your marine tank, then the damselfish is the perfect choice for you. It is small, challenging, and readily available.
Blue Damselfish are perfect for beginners because they are incredibly resilient to common beginner mistakes such as a low nitrogen cycle.
Just make sure to do your research before buying a Damselfish because there are over 250 variants; some may have special requirements that we may not have covered in this guide.
