The green chromis (Chromis viridis) or blue-green chromis is one of the most popular fish species in the aquarium trade. They rank at the top courtesy of affordable prices, superb coloration, boldness and energy, and shoaling behaving, allowing them to get purchased in large numbers to create a schooling effect in the tank. They belong to the same family as more aggressive damselfish, but they missed out on that punchy nature. Instead, you get a delightful species that won’t cause any trouble. (Hint: this also makes them popular with beginners) If you haven’t considered adding one (or ten), you will by the time you finish reading!
Table of Contents: Green Chromis
As you probably guessed from their name, green chromis catch the eye with their iridescent blue-green scales. Get a school, and you’ll see pops of green as they move throughout the tank. They’re easy enough to manage, as you’ll see in the links below. That doesn’t mean you’re off the hook when it comes to care, though. Managing a school comes with its own challenges. So if you haven’t purchased a shoal before, you might want to stick around for the entire article.
Green Chromis: Natural Habitat
In the wild, green chromis inhabit coral reef areas in the Indo-Pacific. Divers encounter shoals of the saltwater species from Madagascar, out to the Philippines, and even around Hawaii. They’re found in lower water flow regions such as lagoons, darting around searching for their next meal. You won’t find them too deep, either; they prefer shallow waters (a maximum depth of 36 feet/11m).
You can’t miss green chromis, even if they lack any discernable patterns on their scales. The trademark bluish-green color stands out. Depending on the lighting, you can see a range from Granny Smith apple green all the way to vibrant blue (and everything in between). They’re iridescent, with a built-in shimmer to the colors. And the fins are transparent. It makes these fish gorgeous to watch as they dart around a reef (or your tank). You’ll also note a LONG dorsal fin, stretching from just behind the head all the way to the tail.
During the spawning season, male green chromis take on a yellow hue. It’s the only way to tell the difference between the two sexes. Otherwise, pairs look identical. (A difference when you consider plenty of the other species out there where only the male gets the colorful end of the palette)
Out in the ocean, green chromis grow up to 4 inches (10.2cm) long. Captive specimens usually only reach around 3 inches (7.6cm), though (a touch on the shorter side). However, they’re FAST growers. Even in a home aquarium, these stunners tend to add to their length in record time. (So don’t be fooled when you see the tiny juveniles in your local fish store)
Out on the lagoons and reefs, green chromis survive for anywhere from 8-15 years. And, with the proper care, you’ll see similar lifespans in a captive environment. Plenty of hobbysits report their chromis surviving for over a decade. However, that’s with proper water conditions, a healthy shoal environment, and adequate tank space. If you’re not staying on top of the care needs, you may see your green chromis falling on the shorter end of the spectrum.
Setting Up the Ideal Green Chromis World
Green chromis live and hide in large coral aggregations. If you want to keep your blue-green fish happy and healthy, you should replicate that environment. A tank full of SPS corals will create a stunning display (and that’s often what we try to create when we purchase these beautiful fish). Don’t forget to add plenty of live rock, too. Chromis feed on algae, and they’ll graze over the nooks and crannies provided by the natural rocky structures.
You don’t want to go overboard with the aquascaping, though. Green chromis are active, shoaling fish. They need room to swim. So while it’s fine to build up the bottom of your aquarium, leave the middle and top open for swimming space. How much room do you need? That depends on the size of the school you opt for. While peaceful, you don’t want your chromis to feel like sardines. Allow a loose formation to move smoothly around the tank.
A low current is all you need when setting up powerheads. Remember, green chromis prefer lagoons – not the drop-off. If the water flow goes too high, your fish may end up stressed or injured. They’ll get plenty of exercise exploring the tank; you don’t need to go overboard creating an underwater treadmill.
Green Chromis Tank Size
Although not the largest reef fish in captivity, green chromis need a tank that balances swimming space, coral, and live rock. Live Aquaria recommends a minimum tank size of 30 gallons (114L). That’s enough to suppose a small school without creating problems. However, if you’re looking to create a community tank with mixed species, you’re going to need to increase your aquatic footprint.
You’ll also want to invest in a robust filtration system. Green chromis don’t create a ton of waste (they’re not carnivores or messy eaters). But they ARE sensitive to changes in water conditions. If ammonia or nitrates start climbing, you’ll end up with sick fish. And the larger your shoal, the greater the risk of values creeping up. It’s a delicate balancing game. You want your green chromis to stay in a school for their social needs, but you don’t want an unhealthy tank. A solid filtration system (or sump tank) will do the trick.
Are Green Chromis Reef-Safe?
As you might have guessed, you’re in the clear adding green chromis to your favorite reef tank. While the species order from the omnivore side of the menu, they don’t have a taste for coral polyps. Instead, they prefer to graze on the algae that tend to spring up around your favorite frags and colonies. And since the school swims in the middle and upper levels of the tank, that activity won’t disturb even the most delicate tentacles.
It’s one more reason hobbyists love this fish!
Green Chromis Diet
Green chromis are omnivores, or – more specifically, planktivores. They feed on planktonic offerings such as fish eggs or larva, copepods, mysis shrimp, etc. As they swim around the aquarium, they scavenge for their next meal (and that includes the algae that pop up on your live rock). You can offer them any of these tasty morsels without a problem. Chromis also accept commercial pellets and flakes. A varied diet will keep those blue-green colors shimmering (not to mention ensure your fish stay healthy).
Green chromis remain active throughout the day. This translates to a HIGH metabolism. If you don’t want them to drop weight, you should feed them several times a day (at least three). Small amounts – enough for everyone in the shoal, though – will do the trick. You don’t want leftovers hanging around to foul the water. If you hold off and only offer a single large meal, you may notice your green chromis becoming lethargic. That’s a red flag that they’re not getting enough food.
Green Chromos Behavior and Tank Mates
Green chromis belong to the damselfish group. Their cousins almost always come with warning labels regarding aggression. But these blue-green beauties break the mold. They’re peaceful, avoiding issues with their tank mates. The most you’ll see is an occasional skirmish over the shoal’s pecking order. And if you’ve provided enough tank space, even that shouldn’t prove an issue.
As schooling fish, you need to keep chromis in groups. At a minimum, you want six fish in your tank. You’ll avoid stress concerns, allowing the individual fish to feel confident and exhibit their natural behaviors. You WANT to see the fish swimming back and forth throughout the day. If they’re hiding in the rockwork, you may need to add to the group. Of course, that can present additional problems. Once you have an established school, you have a pecking order. Dominant fish will chase and even harass new, submissive, or smaller fish.
It’s best if you start with the anticipated shoal size FIRST. Then you won’t have aggression develop down the line. In the March/April 2016 issue of CORAL Magazine, “Piscine Passels: Social Fishes for the Marine Aquarium” by Scott W. Michael, he recommends keeping the minimum of six green chromis to disperse aggression. Although he does suggest groups TWICE that size are more likely to thrive.
Otherwise, green chromis are generally community-friendly, reef-safe fish. As long as you plan to house them with other peaceful species of similar sizes, they’ll do well:
Breeding Green Chromis
As you maintain green chromis in shoals, breeding the species isn’t difficult. Of course, determining whether you have males or females gets tricky. You’ll need to wait until spawning season rolls around to see if any of your fish take on that yellow hue. And if you have predators present in the tank? That may not happen at all. Spawning requires a healthy, SAFE environment.
Male chromis prepare a nest in the substrate. Females (yes, sometimes more than one) then lay eggs in the nest. The male then fertilizes and guards the eggs. If you see him eating the eggs, don’t worry. The eaten eggs were unfertilized or died. (And, really, he’s doing hard work!)
Chromis eggs hatch after 2-3 days. And, unhappily, the male leaves his post at that point. But the fry remain susceptible to predation until they’re around 47 days old. If you want to improve the odds of your green chromis breeding operations, gently transfer the fry to a nursery tank. You can then raise them on brine shrimp nauplii. Once they’re large enough to compete with the adults in your display tank, they can move “home.”
Pros and Cons
All in all, I’m a big fan of the green chromis. They’re a relatively docile and inexpensive species. And they often appear early on the list for most people starting out in the saltwater aquarium hobby. However, no fish is perfect. So before you rush out to start your shoal, make sure you look at EVERYTHING that goes into the care of this blue-green stunner.
- Green chromis are hardy fish that are relatively inexpensive – even when you need to purchase a shoal of at least six.
- Chromis exhibit active and bold behaviors throughout the middle and upper levels of the tank.
- Chromis are reef-safe; they won’t attack polyps – though they will feed on algae throughout the aquarium.
- Green chromis may carry parasites (so use proper quarantine).
- While peaceful, chromis will show aggression within the school as they determine their pecking order.
- Chromis are easy to breed, but the fry remain vulnerable for close to two months, requiring a separate nursery tank.
Green chromis catch the eye. Maybe they come with a few little quirks with their management, but nothing TOO serious. So who wouldn’t want to add them to their collection? And in case you need a little more convincing, you’ve got it. You’ll find a few last-second gems below.
To start with, how about a YouTube video with everything you need to know about green chromis?
Have a fantastic community tank planned but need better insight into the best tank mates for green chromis? No problem:
Curious about those OTHER damselfish? The ones with the not-so-savory rep?
Green chromis are lovely community fish that won’t cause any trouble in a reef tank. They DO need an aquarium with pristine water conditions. And you’ll need to maintain a school of at least six if you want to minimize their stress levels and promote natural behaviors. But aren’t those minor inconveniences worth a stunning display tank of blue and green flashing scales? Of course, they are!
Do you have chromis in your tank? If so, leave a comment with a picture and show them off!