Chromis and damselfish are among the most commonly kept fish in the hobby, because of their bright colours, small size and hardiness. They are from the family Pomacentridae and live on coral reefs all over the world. Chromis and damselfish range in both size and temperament, with some species being larger and more aggressive than others. Always consult your OATA retailer before purchasing any chromis or damselfish to ensure they will mix with current tank mates.
Water requirements
Chromis and damselfish are usually undemanding of water chemistry and their suggested parameters are shown below. These parameters are a general guide for this group of fish, so it is important to check with your OATA retailer for any species-specific requirements before purchasing. Please also note that if keeping these fish in a reef aquarium, some parameters will need to be altered to accommodate more sensitive species.
- Salinity: Between 1.020-1.025
- Temperature: Between 24-26°C
- pH: 7.9-8.3
- Ammonia: Zero mg per litre
- Nitrite: Zero mg per litre
- Nitrate: Not to exceed 50 mg per litre
- Carbonate hardness: Hard (8-12°dkH)
- Calcium: Between 380-450 ppm
- Magnesium: Between 1250-1350 ppm
Biology
Both chromis and damselfish usually remain relatively small, very rarely growing over 10 cm. However, some of the larger species of damselfish may grow nearer to 15cm. There are many species of damselfish available, but some of the most common are the yellow tail blue damsel (Chrysiptera parasema), domino (Dascyllus trimaculatus) and humbug (Dascyllus aruanus). The most popular chromis species is the green chromis (Chromis viridis). Regardless of species or colour, these fish can live for many years in a well-matured set-up with good water quality.
In the wild, chromis and damselfish can be found in groups near areas of hard coral growth in which they quickly take shelter if they notice a threat. Some damselfish species ‘farm’ a patch of algae and will defend it aggressively in the wild and are therefore territorial in aquariums. There are some species of damselfish which are less aggressive, but most display some level of territoriality. Chromis are shoaling fish and should be kept in groups of at least five in the home aquarium, but more is better. Chromis kept singly or in too small groups will often become stressed. Some damselfish will prefer to live alone, whereas some will do better in large groups. Ask your OATA retailer for guidance.
It can be difficult to identify the sex of most chromis and damselfish species unless they are in breeding condition, although some species may have obvious male/female differences in colour or finnage.
Aquarium requirements
As a general rule, you should within reason, buy an aquarium as large as possible. It is recommended that an aquarium of at least 60 litres is used for a single damselfish (it is recommended chromis are not kept alone). To keep a group of damselfish or chromis, a much larger aquarium of at least 200 litres is recommended. A larger aquarium will also provide more stability to environmental conditions such as temperature and water quality. Whatever the size, a filter is essential. For marine set-ups this can be in the form of live rock with sufficient water flow, an internal or external filter, or a sump-based filter. A protein skimmer can also be beneficial for maintaining water quality as it will help to remove dissolved organic waste before it can break down into more harmful substances.
Chromis and damselfish are relatively undemanding in terms of aquarium décor. Either live or artificial rockwork is good as it provides a site for them to use as cover. If keeping some of the more territorial species, ensure the rockwork is complex to provide sites for all individuals to hide in, alongside other species you wish to keep. Chromis are more active and will spend a lot of their time swimming in the open, so ensure there is enough space for them to swim freely. A thin layer of coral sand (approximately 2cm) is useful to make chromis and damselfish feel secure and to maintain carbonate hardness levels. There should be a moderate water flow to provide good surface movement and to ensure detritus doesn’t accumulate.
A heater is required to maintain a suitable temperature all year round. To minimise fluctuations in water temperature, the aquarium should not be situated near any draughts or heat sources. It should also be out of direct sunlight and away from loud noises, vibrations and sudden movements. Overhead tank lighting is recommended to maintain a correct day-night cycle. This will not need to be particularly bright for chromis or damselfish alone but may need to be brighter if keeping with coral species – see our coral care sheets for more information.
Water testing kits are essential so that water quality can be checked on a regular basis (once a week) to ensure it does not slip below the water requirements stated earlier.
Introducing your fish
Before adding any fish, seek advice from your OATA retailer to make sure that your aquarium is an appropriate size for the chromis or damselfish you would like to keep. Check that the water quality in your aquarium is suitable i.e. levels of ammonia and nitrite are zero. Only increase the number of fish you have in your aquarium slowly as the population of beneficial bacteria established when maturing your aquarium filter need to increase every time more fish are added and feeding increases. Overstocking or stocking your aquarium too quickly can result in ‘new tank syndrome’. This occurs when there are not enough nitrifying bacteria to cope with the increased waste from the fish, leading to unhealthy levels of ammonia and nitrite, which may cause fish to become ill or die.
Healthy fish have clear bright eyes, undamaged fins, intact scales, no ulcerations or bumps, appropriate swimming behaviour and steady breathing. Do not purchase a seemingly healthy fish if sickly fish are present in the tank with it. Signs of disease can include clamped fins, flicking against gravel or décor and shimmying (shaking). Diseases can be easily carried by fish that do not show any clinical signs. If in doubt, ask your OATA retailer for advice as they will have in-depth knowledge and experience.
Your OATA retailer will usually sell your fish to you in a plastic bag, try not to keep them in this for too long. Once purchased, take your new fish home as quickly as possible because fish are easily stressed by bright lights, extreme temperatures, noise and movement.
Once home, your fish will need to acclimatise to their new environment and a common method of doing this is known as the ‘floating bag’ method. Switch off the aquarium lights and take the bag containing your new fish out of its outer wrappings carefully, avoiding exposure to bright light. Float the bag in the water of your tank to ensure the temperature in the bag is the same as the aquarium water. After 10 minutes, slowly introduce small amounts of aquarium water into the bag containing the fish for up to 30 minutes. Once complete, carefully release the fish into the aquarium whilst introducing as little bag water into the aquarium as possible. This is especially important if keeping fish with any invertebrate species as some retailers run copper in their systems, which is toxic to invertebrates. After this, dispose of the bag and any excess water appropriately.
For sensitive species or to ensure retailer water does not enter your aquarium, a better method might be the use of drip acclimation. This could be achieved by keeping the fish in the container in which it is sold and a small airline siphon started to drip water into the container, slowly changing the water parameters to that of the aquarium. Ensure that the temperature does not fall too low during this procedure. Once conditions match, carefully net the fish from the container into the aquarium. Dispose of the water in the transport container appropriately. Monitor your new fish carefully for the first week, paying particular attention to water quality. If in doubt, contact your OATA retailer for advice.
If possible, quarantining new livestock in a separate aquarium for at least a week before they enter the main tank can help reduce any risk of disease spread from new inhabitants. Ask your OATA retailer for advice on this topic.
Maintenance
At least once every week, a partial water change of 25% is strongly recommended (a siphon device is useful to remove solid waste from the gravel). Filters should be well maintained, with regular checking and cleaning to prevent blockages. If the filter needs cleaning, do not run it under the tap because any chlorine or chloramine present may kill the beneficial bacterial population that has established in the media. Instead, it should be rinsed lightly in the tank water which is removed during a partial water change as this reduces the amount of bacteria which are lost. Protein skimmers should be regularly cleaned to maintain their performance.
Good husbandry is essential as chromis and damselfish can be stressed by even the smallest amounts of ammonia and nitrite which may then cause them to develop various diseases. Test the water to monitor the ammonia, nitrite and nitrate levels, together with pH and carbonate hardness every week, especially during initial set-up and after adding extra fish. It is also important to regularly monitor salinity and use reverse osmosis water to replace any water lost through evaporation.
What to watch out for
All fish will have slight variations in their behaviour or appearance, but keeping an eye on any changes in the following will help to identify any potential problems before they become a real health issue:
- swimming behaviour – hanging at the surface, sitting on the bottom or erratic swimming
- colour – turning a darker or paler colour than normal
- temperament – changes in level of aggression or hiding more than normal
- breathing – gill covers moving at a slower or faster rate than normal
- appearance – development of white spots or fluffy growths, loss of fins or scales
- condition – increase or decrease in body weight and condition
- feeding – reduced intake or lack of interest in food
If you are concerned about the health of any of your livestock, then test your water quality and contact your OATA retailer for further guidance.
Feeding
Chromis and damselfish are omnivorous and require a wide range of foods to be in their best health. A good quality flake or pellet will fulfil most of their nutritional needs, but this should be supplemented with frozen feeds such as mysis shrimp, enriched brine shrimp or red plankton. In the wild, damselfish and chromis may also feed on algae, and so they may graze on any algae which is offered to herbivorous species or grows in the aquarium. Chromis and damselfish should only be fed what they can eat within a few minutes, twice a day. Take care not to overfeed as this can lead to a build-up of uneaten food which breaks down releasing toxic waste into the water. If in doubt, ask your OATA retailer for advice on appropriate feeding levels.
Compatibility
Chromis species are generally quite peaceful, although they may squabble between each other, and will mix well with other relatively peaceful species. Damselfish vary in temperament with some being relatively calm and mixing well with other species, whilst others grow large and will attack other fish. The more peaceful species, such as Talbot’s damsel (Chrysiptera talboti) or yellow tail blue damselfish (Chrysiptera parasema), can be kept in a community aquarium with other hardy fish. Other species such as dominoes or humbugs, will need to be mixed with much tougher species like large angelfish, triggerfish and pufferfish. Always consult your OATA retailer before mixing chromis or damselfish with any other species.
Breeding
Chromis and damselfish may spawn in the home aquarium. The male and female will clean a site, on which the female will lay eggs for the male to fertilise. They will fan the eggs to provide water flow around them and will remove any non-viable ones by eating them. Unfortunately, the delicate larvae are unlikely to survive in a home aquarium as they will get sucked into filters and pumps or eaten by other aquarium inhabitants. They also require specific live feeds and so a specialist set up is required to raise them to adulthood. Some species of damselfish exhibit some parental care and look after their young in a similar way to dwarf cichlids, but this is very unusual.
Checklist
Before purchase make sure:
- You have the appropriate equipment and position for the aquarium.
- You have researched all the species in which you are interested and your final choices are all compatible.
- You are familiar with how to transport and release your fish.
- You are aware of the daily, weekly and monthly maintenance your aquarium will require.
- You are prepared to look after your fish properly for the duration of their life.
Shopping list
- Glass or acrylic aquarium
- Filter*
- Heater
- Lighting (required for live plants)*
- Gravel or sand
- Tap water conditioner/dechlorinator
- Aquarium salt and a hydrometer or refractometer
- Access to reverse osmosis water or a reverse osmosis unit
- Water testing kits (ideally ammonia, nitrite, nitrate, pH and water hardness)
- Live or artificial rock
- Protein skimmer* (optional but recommended)
- Ultraviolet steriliser (optional but recommended)
- Gravel cleaner/siphon cleaning device (recommended)
- Aquarium decorations and/or live plants
- Bucket for water changes
*may be included in branded aquarium sets but can be purchased separately. Water testing kits (ideally ammonia, nitrite, nitrate, pH and water hardness)
Before purchase make sure:
- The aquarium is of a suitable size that ideally can accommodate the fish once they are fully grown.
- Water parameters are as advised in this leaflet.
- Aquarium is cycled and ready to receive fish.
Top tips
Always buy…
test kits and regularly check the water for ammonia, nitrite, nitrate and pH. This will allow you to make sure the water in your aquarium is not causing welfare problems for your fish.
Establish a routine…
for testing the water in your aquarium. Record your results to enable you to identify fluctuations quickly. Also check the temperature of the water.
Maintain…
the water in the aquarium within the accepted parameters highlighted above. You may need to do regular water changes to achieve this.
Always wash your hands…
making sure to rinse off all soap residues, before putting them into your aquarium, or use long sleeved rubber gloves. Wash your hands again afterwards and certainly before eating, drinking or smoking.
Never siphon by mouth…
A fish tank can harbour bacteria which can be harmful if swallowed. Buy a specially designed aquarium gravel cleaner which can be started or primed without the need to place the siphon in your mouth.
Five Welfare Needs Checklist:
The Animal Welfare Act 2006 states that all pet owners have a legal duty of care to their pets. Anyone who is cruel to an animal or is found not to be providing the five animal welfare needs, as listed below, can be prosecuted.
- A suitable environment e.g. appropriately sized tank (with water heater if tropical set up) within a suitable location in your home.
- A suitable diet which meets the needs of your chosen fish.
- Behaviour – Fish are able to exhibit their normal behaviour e.g. hiding places for timid fish, enough room for fish to swim freely.
- Companionship – Ensure you know whether your chosen fish need to be kept with, or apart from, other fish.
- Health – Protected from pain, injury, suffering & disease e.g. you are aware of the daily, weekly and monthly maintenance that your aquarium will need.
Remember...
Water quality test kits are a necessity not an optional extra.
You must be prepared to look after your fish properly for the duration of their life and provide an aquarium which can accommodate your fish when fully grown.
Never release your aquarium animals or plants into the wild. It is illegal and for most fish species this will lead to an untimely and possibly lingering death. Any animals or plants that do survive might be harmful to our native countryside. Take care to properly dispose of any soiled substrate (e.g. sand or gravel) water or decorations so that non-native organisms do not enter natural watercourses.
