Marine Betta Reef Safe

Is A Marine Betta Reef-Safe?

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Although it’s called a Marine betta, this is a saltwater fish species and not a freshwater creature at all. In fact, the Marine betta is not related to the Siamese Fighting fish!

So, what is a Marine betta? Would a Marine betta make a good addition to your reef tank, or are these creatures only suitable for a fish-only setup?

Read this guide to find out!

What Is A Marine Betta?

The Marine betta or Calloplesiops altivelis is also commonly called a Comet or Sea betta.

Comets are similar in their basic shape to Plakat betta fish, hence their common name. However, the two types of fish are not related in any way. These are stunningly beautiful, peaceful marine fish with a characteristic black and white spotted pattern that acts as defensive camouflage and a distraction when hunting. 

With the fish’s large, lobed tail fin, backward-facing white eyespot, and clever behavior, these fish are some of the most interesting and attractive fish that you can add to a marine setup.


Callpplesiops altivelis was described by Steindachner in 1903. The fish are commonly called Marine betta, Comet, and Sea betta.

These shy, secretive fish resemble the freshwater Siamese Fighting fish or betta in shape, although these marine creatures are much larger. Callpplesiops altivelis comes from the Plesiopida fish family, including Devilfish, Fairy basslets, Assessors, and Longfins. Generally, this family of fishes is referred to as the Roundheads or Longfins. Although the Marine betta has a similar patternation, it’s not a Soapfish or a Grouper.


Marine bettas are tropical fish found in the Red Sea, Indo-Pacific, and East Africa, ranging down to the Line Islands. You sometimes also find these fish living around the southern tip of Japan, on parts of the southern Great Barrier Reef, and off the coast of Tonga.

Marine bettas are found at a wide range of depths from 10 to 150 feet, inhabiting pinnacle reefs, lagoon patch reefs, and fore-reef slopes. Here, the fish hide in crevices, caves, and along drop-offs. These are nocturnal hunters, staying hidden from predators in holes and under overhangs during the daytime, often with shrimp, pygmy angelfish, and Spotfin Lionfish.

These predatory, carnivorous fish hunt small fish and crustaceans.

In their wild habitat, Marine bettas live in small groups or in pairs. Generally, these are shy, reclusive fish. However, males will guard their eggs, using their dorsal fin to conceal the eggs from predators and positioning themselves between intruders and their precious clutch of eggs.

What Do Marine Bettas Look Like?

Adult Marine bettas are dark brownish-black covered with small white spots, forming rows on the fish’s body. The fish’s large eyes are completely obscured, even having white spots on the iris! 

On the back of the fish’s dorsal fin over the base of the caudal, there’s a large black spot or false eye that’s designed to confuse prey and deter predators. The prominent eyespot and the edges of the finnage are outlined in yellow and pale blue. 

Although they look the same, mature male Marine betta fish are generally larger than females.

What Size Are Marine Bettas?

Marine bettas can reach 8 inches long in the wild. However, captive specimens are somewhat smaller, usually growing to around 7 inches.

Male specimens are usually larger than females.

What’s The Lifespan Of A Marine Betta?

The lifespan of wild Marine bettas is unknown. However, in captivity, Marine bettas can live for ten years or more, provided they are fed a correct diet and kept in a stress-free environment.

Fascinating Behavior

Marine bettas exhibit the most fascinating behavior when they’re hunting and as a defense against predators.

The fish tips its body forward with its head lowered. The pectoral fins are spread, and the tail fin is curled and used to propel the fish toward its prey. The Comet’s false eyespot totally confuses the prey, which usually flees from the perceived danger, straight into the fish’s cunningly camouflaged mouth!

If the Marine betta is the hunted rather than the hunter, it will slide headfirst into a crevice, leaving its rear end sticking out of the hiding place. This marine master of disguise then assumes a clever pose that makes it look like a White Mouth Moral eel (Gymnothorax Meleagris). That’s almost always enough to frighten off most predators, leaving the fish unharmed. 

Diet And Nutrition

Most Marine bettas are wild-caught, which makes them challenging to feed at first. Ideally, you need an established tank with plenty of live rock and natural foods. 

Basically, to feed the fish, you have to work out where the fish is hiding in the aquarium and push live foods into the hideout. Eventually, you can persuade the fish to eat frozen food and prepared meaty foods by putting the morsels of food directly into the pump stream. That tricks the betta into chasing the food, mistaking it for live prey. 

These fish are carnivores, feeding on small fish and crustaceans. When first caught, you need to feed the fish gut-loaded mysis or feeder shrimp. Once the bettas are acclimated, you can give them prepared foods, such as fortified brine shrimp, scallops, fresh fish, minced shrimp, baby shrimp, and frozen foods.

Although some hobbyists have reported that they have weaned their Marine bettas onto a diet of fish flakes and sinking fish pellets, it’s recommended that meaty protein forms most of the fish’s diet. A basic diet of dried food is not what the Marine betta eats naturally and can cause health issues.

How Often Should I Feed Marine Bettas?

Ideally, you should feed your Marine bettas several times a day, offering what the fish will eat in a couple of minutes at each feed.

Since these fish are primarily active under cover of darkness, you should feed the fish just before and after lights-out. To maintain that feeding regime, it’s recommended that you invest in an automatic fish feeder. That way, you can load the feeder’s hopper with the right amount of prepared food and set the timer to dispense the preferred food at the appropriate time.

Marine Betta Care Guide

Habitat Requirements

Tank Size

If you only want to keep one Comet, a 55-gallon tank should be adequate as minimum tank size. However, if you want to keep more than one fish, you need an aquarium of at least 100 gallons.

These fish generally tend to hang out in the mid to lower regions of the water column away from the lights.

Tank Decorations

As mentioned above, these are very shy, nocturnal fish. So, you need to provide plenty of hiding places where the Comets can get out of the light and hide away from their aggressive tank mates.

Include plenty of mature live rock to help new wild-caught Marine bettas settle in and adjust to life in the aquarium. Tank-bred Comets also appreciate the inclusion of the live rock in the setup, as it provides a nice source of their favorite food for them to graze on between feeds.


The Comet doesn’t appreciate bright aquarium lights. So, blue lights are a good choice in a fish-only tank. Be sure to leave shaded areas where the fish can escape the light if they venture out when the tank is illuminated.


A sandy substrate strewn with rocks is perfect for these reef-dwelling fish.

Water Parameters

As with all fish species, Marine bettas need a stable environment with the same water parameters they are used to enjoying in the wild environment. These fish are actually much hardier than many marine species and generally acclimate well to aquarium life.

The water temperature should be between 72˚F and 81˚F. Water pH should be in the range of 8.0 and 8.4, with a normal salinity of 1.023 and 1.025. 


Marine bettas aren’t fussy about water movement, but we recommend you don’t have the powerhead directed into the fish’s preferred area, as a strong current might stress the fish.

What Are Good Tank Mates For Marine Bettas?

In the spacious wild environment of a tropical reef, Marine bettas live in small groups. But what about in the aquarium?

Can Marine Comets Live Together In The Aquarium?

Although Marine bettas live in small groups in the wild environment, males will fight in the aquarium setting. If you’re unsure what sex your fish are, you need to keep them in a tank that’s at least six feet in length. That gives the fish plenty of space to avoid each other if they want to.

If you buy a breeding pair, they should be happy in a 75-gallon tank. 

In all cases, when keeping multiple Marine bettas, be sure to include plenty of hiding places where the fish can get out of each other’s way and establish a territory.

Tank Mates

Although the Marine betta is generally regarded as a peaceful fish in a saltwater tank, the fish is a predator by nature. However, they will prey on small fish or crustaceans that will fit into their mouths. For that reason, avoid keeping Comets with skinny, thin fish like juvenile Flasher wrasses or Clown gobies.

Fish that can make suitable tank mates for Marine bettas include:

  • Fairy wrasse
  • Mature Flasher wrasse
  • Clownfish
  • Anthias
  • Dwarf Angelfish
  • Jawfish
  • Small Hawkfish
  • Large blennies and gobies

It’s safest to add the Marine betta as a juvenile and when those other smaller fish are fully grown. That tactic helps to establish a harmonious community tank where all the tank inhabitants regard each other as friends, not food!

Fish To Avoid

Aggressive tankmates or large-sized fish should not be housed with the Marine betta, as the smaller betta will almost certainly be bullied. So, avoid keeping fish species, including:

  • Triggerfish
  • Large Dottybacks
  • Damselfish
  • Lionfish
  • Groupers

Also, fast swimmers, such as Tangs, large Angelfish, and the like, will intimidate the Marine bettas, preventing them from emerging from their hiding places to feed.

Are Marine Bettas Reef-Safe?

Marine bettas are considered to be safe for a reef aquarium, with a few caveats. Basically, the Comet won’t eat polyps or corals, although they are carnivorous predators that will prey on ornamental shrimps and small fish.

That said, Marine bettas don’t appreciate the bright lighting that many corals need and will probably spend much of their time hiding in a full reef tank. You can overcome that problem by only putting corals in the center of the tank, leaving the perimeter and corners dark for the Comet.

Marine bettas are carnivorous predators that eat small crustaceans, especially shrimp. If Cleaner shrimp are in the tank when the juvenile Marine betta is added, all should be well, and the shrimp should be left alone. However, if you introduce Ornamental shrimp after the Marine betta has settled in, your shrimp will surely disappear one by one!

Snails and starfish such as Brittle stars won’t be bothered by the Marine betta.

Health And Disease

Marine bettas are hardy and disease-resistant fish that are pretty much bullet-proof when compared with many other marine species and are very hardy fish. In fact, these are one of the only species that doesn’t succumb to Crypt even if every other fish in the tank has it.

Minor injuries seem to heal incredibly quickly, too. Even common bacterial infections are reportedly rarely seen in Marine bettas.


Marine Betta

It’s challenging to breed Marine bettas in captivity.

In the wild, the fish produce strings of between 300 and 500 tiny golden-brown eggs that adhere to the underside of an overhang or cave. The male Comet guards the eggs, fanning them to keep them aerated and free from debris—the eggs hatch after around five or six days. The well-developed fry can begin feeding right away and grow quickly, reaching up to .32 inches in length in just 14 days. 

At 16 days old, the fish start to develop one white spot on either side of their bodies. By two months, white spots begin to form on the juvenile Marine betta’s face, although the single white spot is retained until the fish are around seven months old.

Originally, all Marine bettas that appeared in the trade were wild-caught. However, commercially bred fish have been available since 2012.


You most likely won’t find Marine bettas for sale in your local fish store, although some marine specialist outlets do have them from time to time.

The best place to source these fish is via online stores, where they retail for around $80, depending on the age and size of the fish.

Although their hardiness makes these beautiful saltwater fish appealing as beginner fish, their price can be offputting for newbies.

In Conclusion

The Marine betta or Comet is a strikingly beautiful fish that makes a lovely addition to an established, mature marine aquarium.

These fantastic fish are peaceful, hardy, and relatively easy to care for once they have acclimated to a non-live diet, making them excellent for a marine community fish setup.

Do you have a Marine betta? Did you successfully breed these gorgeous fish in your aquarium? Tell us your story in the comments box below.

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