Protonibea Diacanthus (Blackspotted Croaker)

protonibea diacanthus

Last updated on July 12th, 2022 at 08:55 am

In the world of saltwater aquariums, Protonibea diacanthus is commonly referred to as a blackspotted croaker or ghol fish. It’s relatively easy to keep these popular fish in aquariums, but they do need special care that differentiates them from other saltwater fish you might want to keep. From their housing requirements to their feeding habits, here’s everything you need to know about keeping blackspotted croakers in your aquarium.

The protonibea diacanthus has been found in tropical and subtropical waters in both the Pacific and Atlantic Oceans. It’s mostly found in coastal areas such as bays, estuaries, and lagoons, but it can also be found in deeper offshore waters near reefs and shipwrecks. These fish are considered to be reef-dwelling species, as they typically live in areas with dense coral populations.

Explorer and naturalist Alexander von Humboldt, who made extensive studies of South American natural history and geology in the late 1700s, first described Protonibea diacanthus (blackspotted croaker) in 1807.

Origins and descriptions

protonibea diacanthus

Protonibea diacanthus is a saltwater fish native to Atlantic waters. It is also known as blackspotted croaker and commonly sold under a number of common names including bluespot flounder, eastern yellow-fin bream, eye bream, etc.

Blackspot flounders tend to grow no larger than 5 inches in length but can reach weights of up to 1 lb. Their normal diet consists primarily of zooplankton, tiny crustaceans, and small benthic worms that live in shallow sandy areas. Protonibea diacanthus are collected commercially off Florida’s East Coast throughout much of its range.

Species profile

The blackspotted croaker, Protonibea diacanthus, is a member of the family Sciaenidae, which also includes drums and croakers. These fish are benthic carnivores that consume shrimp, mollusks, small crabs, worms, snails, and other crustaceans. The blackspotted croaker lives in tropical marine waters throughout many regions of South America. Some subspecies live in brackish waters.

It has been introduced to several parts of Southeast Asia as well. They typically inhabit sandy areas near shallow reefs and seagrass beds, but they have also been known to hide beneath mangrove roots or rocks on muddy bottoms during daylight hours. Juveniles tend to favor inshore lagoons with dense seagrass cover. In general, they avoid murky or turbid water conditions; however, they have been observed swimming at depths up to 90 feet at night.

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Protonibea diacanthus dwell in shallow, sandy waters with dense seagrass. They can often be found in estuaries, ocean bays, mangrove-lined creeks, or lagoons. While they do prefer water temperatures to remain a consistent 79 degrees Fahrenheit or warmer during the breeding season, their temperature tolerance is fairly high—they will survive a range of 55 degrees all the way up to 86 degrees. However, most pet owners are happy to report that these fish don’t seem to mind having warm water year-round!

Protonibea diacanthus size

The average length of this fish is 1.5 meters (150 cm).

Protonibea diacanthusv tank size

As adults, blackspotted croakers need to be kept alone in a tank at least 200+ gallons in size. Blackspotted croakers are most comfortable when kept in tanks with plenty of hiding places like caves or rock formations.

Tank set up

The blackspotted croaker is an active species that needs a spacious environment. A minimum of 200 gallons is needed for 1 blackspotted croaker, but more room is always better. This fish likes to have hiding spots created by large plants, rocks, or driftwood. They will also use these areas to rest from time to time. Having multiple caves will allow them to choose different places at random times throughout the day, providing them with enough variety in their aquarium setup.

If you are able to go larger than 200 gallons with your aquarium, do so! These fish get pretty big as adults and need space for themselves as well as all of their tank mates. I prefer using 5-gallon buckets turned upside down as caves when breeding tanks are limited on decorations. As long as there are plenty of other caves they can hide in, they will gladly utilize these buckets.

Remember, if they don’t like it, don’t force it upon them – try something else! When creating your aquarium world consider how many creatures you want swimming around together. Be sure to give ample rooms for each creature and don’t overcrowd your aquarium. Overcrowding creates aggression within creatures which can lead to illness, decreased health, and death.

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Protonibea diacanthus tank mates

This fish will likely eat invertebrates that live in a saltwater aquarium. In an aquarium, it can be kept with ornamental shrimp, small crabs and snails, sea stars, and other small herbivores. Keep in mind that its predatory nature means it may attempt to eat anything it can fit into its mouth! If you keep a croaker with other fish species, make sure they are too large to be swallowed whole by your pet.

Otherwise, there is a chance of injury or death for other aquarium inhabitants when startled; thus, it is best to keep them alone. Also, remember that their ability to hunt smaller fish and their tendency towards squirmy foods makes them unsuitable for tank mates with finicky eating habits.

Protonibea diacanthus breeding

protonibea diacanthus

The blackspotted croaker is a year-round, live-bearer. Pairs will breed in tanks with little more than each other. Males are highly territorial when breeding, and tend to become aggressive towards tankmates as well as their mates. It’s recommended that all fish be removed from the breeding tanks during the breeding sessions; it’s likely that some will get hurt.

After a short gestation period of just under two weeks, females begin depositing eggs onto glass or plants. These should be collected, rinsed thoroughly, then placed into small containers like jars or plastic cups lined with organic material like sphagnum moss. Incubation times vary but average around 45 days.

Be sure that water temperatures don’t fall below 75°F at any point during incubation; if they do fall below 75°F for longer than 12 hours, discard all eggs because they probably won’t hatch properly anyway. Eggs must be rinsed daily to prevent them from rotting on contact with fertilized egg yolk. Within 48 hours after hatching, fry can eat newly hatched brine shrimp or crushed flake food. At one week old, larger foods such as micro pellets can be offered instead of flake food.

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Are Protonibea diacanthus aggressive or peaceful?

Protonibea diacanthus, or blackspotted croakers, are generally peaceful fish that won’t hurt tank mates. However, males can sometimes be aggressive towards each other when kept in an overcrowded tank with little hiding places available. Therefore, keeping these fishes in their own tanks is recommended.

Protonibea diacanthus care

protonibea diacanthus

Blackspotted croakers are very easy to care for. They should be fed a variety of live, frozen, or freeze-dried foods such as krill, silversides, shrimp, squid and chopped fish. They will take most dry flake food but do best on live food. These croakers do best in a 200 gallon or larger aquarium with plenty of rocks and lots of hiding places in caves or under ledges.

Their water temperature should range from 70 degrees F to 80 degrees F with a pH of 7.5 to 8.4. Since these fish can get quite large, over 18 inches, it is necessary that you provide them with a very large tank if you plan on keeping more than one specimen in your tank.

Protonibea diacanthus diet

This species of croaker is an omnivore. They typically eat other fish as well as small crustaceans, worms, plant matter, and anything else they can fit in their mouth. When it comes to feeding time, you can use either live or frozen foods with them. Giving them a variety of foods will help keep them from getting bored during feeding time.

It will also ensure that they get all of the nutrients they need when you are not around to supplement their diet. You won’t need to feed them every day, but at least once every few days should be sufficient. Their diet shouldn’t cause too much problems for tank mates as long as there is enough food for everyone. In some cases, it might be best if one fish eats first before others get any food.

Water parameters

protonibea diacanthus

The ideal water condition should have a pH of 8.0-8.4; temperature: 24°C – 28°C; dH range: 10° – 15°; specific gravity: 1.020 – 1.025 ; and salinity: 18 – 19 ppt

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Protonibea diacanthus lifespan

A typical life span for Protonibea diacanthus is five years, but fish of its genus are known to have a relatively long lifespan. While they may reach maturity at two years old, they’re more likely to live four or five years. In captivity, a blackspotted croaker was observed living over 10 years old.

Parasites and diseases

Blackspotted croakers are susceptible to a variety of external parasites and disease. Parasites such as flukes, skin or mouth worms, or monogeneans can infect blackspotters. In their native range in Southeast Asia, blackspotters are sometimes infected with liver flukes by eating food contaminated with freshwater snails that have been infected by eating rat droppings containing snail eggs infected with liver flukes. To prevent infection, make sure your freshwater fish do not eat snails or other freshwater mollusks.


Many predators to Protonibea diacanthus have been documented. However, most of these are not a concern in home aquariums. The dogfish shark is one such predator that is worth mentioning. This animal can grow to up to 26 inches in length, has no teeth on its upper jaw, but possesses 60 teeth in its lower jaw! It usually feeds on crabs, but it has been known to eat fish as well. When attacking its prey, it will wrap itself around it and crush it with tremendous force.

Do Protonibea diacanthus make good pets?

No. While many people have considered keeping Protonibea diacanthus, these fish do not make good pets. They are difficult to maintain in a home aquarium and require a large tank. In addition, they can be aggressive towards other fish. If you want to keep Protonibea diacanthus as a pet, consider purchasing them from an aquarium store or a breeder instead of catching them from your local body of water.