Groupers are an incredibly diverse species of fish that contain a huge number of variations.
While many grouper fish are not suitable for home aquariums, there are a few that can make attractive additions to a tank…
If you’re thinking of owning a grouper fish, then read on!
Here I’ll be digging into the best species for aquariums, as well as diet, tank setup, tankmates, and breeding.
Do you wonder where these interesting fish are from?
This family also includes sea basses.
The majority of groupers are a dull brown or green color, though some are more vibrant and colorful.
A few specimens such as Nassau groupers can even change their color pattern.
This fish group is varied, but some of the most popular species that are kept in aquariums are swallowtail sea perches, hamlets, and basslets.
Groupers often inhabit temperate waters from the Mid-Atlantic state and Florida all the way down to South America, Central America, and the Gulf of Mexico.
They can also be found in the Indo-Pacific and many other locations across the world.
One of the most well known grouper species is the goliath grouper, which is found in shallow tropical waters in coral reefs and artificial reefs.
It can be seen in the Gulf of Mexico, Florida Keys. the Bahamas, most of the Caribbean, and most of the Brazillian coast.
Groupers are usually found in shallow waters in the Mid-Atlantic state, Florida, South America, Central America, Gulf of Mexico, and Indo-Pacific.
They usually inhabit coral reefs and artificial reefs.
They are one of the top predators in coral reefs and play an important role in coral reef ecosystems around the world by controlling the population of lower trophic level fish.
They have huge, thick mouths that can easily swallow big prey.
Most groupers fish are dull in color, but some come in stunning colors, most of which are popular in home aquariums.
How Do You Tell If They Are Male or Female?
The majority of grouper fish can be quite difficult to sex as there aren’t many external differences between males and females.
However, one of the most interesting aspects of grouper fish is that almost all of them are able to change their sex.
These species are called monandric protogynous hermaphrodites, which means they mature only as females and can change sex once they are sexually mature.
Some grouper varieties grow around a kilogram each year and stay adolescent until they weigh roughly three kilograms, at which point they become female.
The biggest male groupers usually control harems that consist of up to three to fifteen females.
Most grouper fish pair spawn, which allows males to prevent other smaller males from mating.
If a smaller female grouper changes its sex before it can form a harem as a male, then its fitness will decrease.
If a male is not present to mate with, the biggest female that can increase fitness will become male.
Other grouper species are gonochoristic.
This reproductive strategy is related to groups spawning high amounts under habitat cover.
Both of these increase the chances of smaller male groupers reproducing when large male groupers are present.
As I mentioned earlier, most groupers fish are not particularly exciting to look at, coming in a dull brown or green color.
However, some species can be very striking, possessing vibrant and vivid colorations and markings.
These more pretty specimens can come in bright red, blue, orange, green, and black, adorned with equally beautiful patterns.
How Big Do Groupers Get?
Most aquarium varieties of groupers get around 12 inches long, so they’re definitely not small fishes!
Some grouper species are a little smaller than this such as the marine betta grouper, which reaches around 8 inches in length.
Biggest Grouper Species
One of the largest species of grouper is the grouper goliath fish.
It can grow to a staggering 8.2 feet long and weigh as much as 363 kilograms!
The largest hook and line captured goliath was found in Florida and weighed 309 kilograms.
As you can see, some groupers are far too large to be comfortably kept in home aquariums.
Types of Groupers
As groupers are a very diverse family of fish, not all of them are suitable for home aquariums.
In fact, some varieties like goliath groupers are monsters that you certainly don’t want to take out of the ocean!
A lot of grouper species in the Epinephelinae subfamily are popular in home aquariums, so these are the fishes I’ll be focusing on in this article.
That said, some varieties that belong to the Epinephelinae subfamily are rather scary-looking giants that have no place in captivity.
If you’re thinking of keeping a grouper, then here are some varieties that are suitable for home aquarium life.
Bear in mind that some of these specimens can be a little rare, so you might need to do a little hunting if you want to own them.
- Black-Saddled Coral Grouper (Plectropomus Laevis)
- Blue Line Grouper (Cephalopholis Formosa)
- Clown Grouper (Pogonoperca Punctata)
- Coney Grouper (Cephalopholis Fulva))
- Marine Betta Grouper (Calloplesiops Altivelis)
- Panther Grouper (Cromileptes Altivelis)
- Bluespotted Grouper (Cephalopholis Argus)
- Red Louti Grouper (Variola Louti)
- Miniatus Grouper (Cephalopholis Miniata)
- Polleni Grouper (Cephalopholis Polleni)
- African Hind Grouper (Cephalopholis Taeniops)
- Swallowtail Sea Perch (Anthias Anthias)
- Indigo Hamlet (Hypoplectrus Indigo)
- Yellow Assessor Basslet (Assessor Flavissimus)
- Macneill’s Assessor Basslet (Assessor Randalli)
- Harlequin Bass (Serranus Tigrinus)
Can You Raise Them in Captivity?
Some grouper species can be raised and bred in captivity.
However, very little is known about getting these species to breed.
Are They Good for Beginners?
Personally, I would not recommend most species of grouper for beginners.
Compared to other saltwater fish species, groupers can grow pretty big and need a large tank.
There’s also not as much information available about these fish as there is for other saltwater species.
While this shouldn’t be an issue for experienced aquarists who are knowledgeable about keeping saltwater fish, it could be problematic for those new to the fishkeeping hobby.
Additionally, groupers are marine fish, so their care is a little more complicated than freshwater or coldwater species.
If you’ve never kept fish before, I’d advise setting up a tropical or coldwater tank first to help you get to grips with things.
How Long Do They Live?
The average lifespan for a grouper varies between species, but most are rather long-lived.
Marine betta groupers tend to live for around 10 years, while panther groupers can live for over 10 years.
Harlequin basses usually only live for 5 years or a little more.
The Atlantic goliath’s maximum known age is 37 years, but scientists believe these fish can live for 50 or 100 years!
As a high number of groupers live for a considerable amount of years, they require a hefty amount of work and commitment.
You’ll need to make sure you have the time and money to keep groupers in both the immediate and the long run.
Do They Die Easily?
Most grouper species are robust and hardy fish, so they don’t typically have any problems during transport or added to an aquarium.
Unlike some fish that are notoriously sensitive and difficult to keep, groupers are fairly tough.
Diet and Feeding
All groupers are carnivores, so they require a diet that is packed with meat-based foods.
Let’s take a look at the best foods for groupers.
What Do Groupers Eat?
Groupers are carnivorous predators by nature, which makes them truly fascinating fish to watch feed.
In the wild, they will usually eat crustaceans and small fish (or anything that can fit inside their mouths!).
Atlantic goliaths will also eat octopuses, baby sea turtles, barracudas, and even sharks.
They don’t chew but instead swallow prey completely whole!
These fish have incredibly large mouths which allow them to create a powerful amount of negative pressure to suck in whole fish and large invertebrates.
What Is the Best Food for Them?
A good diet is key to keeping groupers happy and healthy.
You should feed them a variety of meaty foods to ensure they get all the nutrients they need for a long life.
When it comes to this predatory fish, feeding them flakes, pellets, or any commercial fish food just won’t suffice.
You need seafood; scallops, squid, shrimp, halibut, and snapper are some excellent food options to keep your groupers satisfied.
Bear in mind that these fish, like all predatory animals, require whole food items to thrive.
You can’t just feed them meat and expect them to be healthy.
Organs, bones, etc., need to be included in your grouper’s diet.
You’ll need to make sure you offer a type of whole animal item at least once or twice a week to your grouper.
Offer them different foods regularly to ensure they get a varied diet.
Some options include frozen baitfish, whole shrimp, crayfish, and frozen silversides.
It’s also a good idea to soak your grouper’s food in a fish-friendly vitamin supplement a few times a week, too.
How Should I Feed Groupers?
When it’s time to feed your groupers, you can simply throw their food into the tank and let them eat.
If there are any leftovers, remove them from your tank as soon as possible to prevent fouling of the water.
How Many Times a Day Should I Feed Them?
You should feed your grouper two times a day: once in the morning and once in the evening.
When feeding them fresh or frozen foods, it’s essential to remove anything uneaten to stop your water from getting dirty.
Leaving shrimp, scallops, etc., in your aquarium for long periods can cause an ammonia spike, which is definitely something you don’t want!
Sandy substrates such as aragonite sand or crushed coral are best for grouper tanks. Gravel isn’t generally used in marine tanks as it lacks buffering capabilities.
A good filter is important for any aquarium, but especially ones that house groupers.
Not only can these fish grow pretty big, but they also have huge appetites.
This means they make a lot of waste.
If your filter lacks strength and power, it won’t be able to effectively clean your tank water. This can cause an array of problems for your groupers.
Types Of Filter
For grouper tanks, I’d recommend using an external canister filter.
Internal filters, hang-on-back filters, and other filter types aren’t the best option for large marine tanks, particularly ones that are home to fish with heavy bio loads like groupers.
When choosing a filter for your grouper tank, make sure you get a model with a suitable flow rate for the size of your aquarium.
As a general rule of thumb, your filter should be able to clean at least four times the volume of your aquarium.
For example, if you have a 200-gallon grouper tank, then you’ll need a filter that has a flow rate of at least 800 gallons per hour (GPH).
I would also advise using a protein skimmer for a grouper tank to help deal with the waste these fish produce.
You might want to consider using a second filter to make sure your grouper tank stays as clean as possible, too.
As groupers naturally inhabit temperate waters, their aquarium needs to accommodate this.
You’ll need to use an aquarium heater when keeping grouper species to ensure your tank water remains at a consistently warm temperature.
Types of Heater
There are a lot of different types of aquarium heaters you can use for a grouper tank, but the most common one is a submersible heater.
It doesn’t matter which type of heater you use as they all have the same function (i.e. heat your tank!), so choose the one that appeals to you the most.
Aquarium lights are another piece of equipment a grouper tank requires.
Unless you’re keeping corals and live plants, you don’t need an overly strong lamp.
Any fish tank light will do the job just fine.
An aquarium light will help replicate a natural day and night cycle for your groupers. Most aquarists keep their lights on for 8 to 12 hours a day.
Any longer than this could stress out your fish.
If you want to keep corals and live plants, then you’ll require a more powerful light with the right color spectrum.
Plants and Decorations
Groupers need plenty of hiding spaces in their tank, so make sure their aquarium has a variety of caves and crevices they can retreat to.
Adding live plants to your grouper tank can also help them feel more comfortable and at ease.
As groupers are carnivores, they won’t pay any attention to live plants, so you don’t need to worry about them destroying your aquascape.
Grouper fish can be kept in reef tanks as they don’t bother corals.
However, they will eat smaller fish and invertebrates if given the chance.
If you want to house a grouper in a reef tank, you’ll need to select your tankmates carefully to ensure they don’t become (expensive!) snacks.
What Size Tank Do They Need?
A large number of groupers can grow pretty big and long, so they require a decent-sized aquarium.
These aren’t the sort of fish that you can keep in a 20-gallon or even 50-gallon!
Most species available to purchase are juveniles, so they won’t be anywhere near their adult length.
However, some species can mature quickly and will rapidly outgrow small tanks. Before keeping a grouper, make sure your tank’s capacity is big enough for their adult size.
Bigger Than Average Fish
Smaller grouper species like the blue line grouper or white-streaked grouper must be kept in at least a 120-gallon tank (larger if you want to add other fish), whereas large species like the lyretail grouper will need at least a 300-gallon tank.
The majority of species can be kept in 200-gallon or 250-gallon tanks.
This gives you enough room for a single grouper and a few other fish.
That said, make sure you check the minimum tank size for the type of grouper you want to get.
Big tanks are always better for these fish, so try to go as large as possible.
Avoid narrow tanks and keep an eye out for tanks with a front-to-back measurement of at least 24 inches.
Additionally, if you want to keep two or more groupers together, then you’ll need a larger aquarium than the minimum tank size for each species.
Like all species of fish, groupers require specific water parameters to survive in the home aquarium.
Salinity and Carbonate Hardness
As groupers are marine species of fish, they require salt water to survive.
For most grouper species, a specific gravity (SG) between 1.020 and 1.025 is sufficient. Carbonate hardness (KH or CH) should be between 8 and 12.
Water changes are an essential part of owning fish, especially groupers.
As I mentioned earlier, groupers have pretty high bio-loads due to their big appetites and messy feeding habits.
The waste your grouper produces will quickly pollute your tank water if you don’t commit to water changes regularly.
Although a strong filter and protein skimmer will help keep your aquarium water clean, that doesn’t mean you can slack on water changes.
Waste Build Up
Ammonia, nitrite, and nitrate will rapidly build up in your tank water without frequent water changes.
All of these can severely affect the health of your fish, and can even result in death.
To stop this from happening, stick to a regular maintenance schedule.
Water Change Frequency
Water changes involve removing around 20% to 30% of the water from your aquarium each week and replacing it with fresh (dechlorinated) water.
However, your tank’s size and the number of fish you own will need to be factored in.
If your tank is small and understocked, then you’ll need to perform larger and more frequent water changes.
Groupers come from temperate waters, so warm water is a must in their tank.
You’ll need to make sure you have a fish tank heater to keep their environment at an appropriate temperature.
Most groupers species do best when kept in tanks between 72 °F to 78 °F.
Water pH Level
While the specific pH preferences vary between species, the majority of groupers like their water with a pH level between 8.1 and 8.4.
It’s a good idea to check the requirements for the species you want to own.
Fish are often thought of as low maintenance pets, but this definitely isn’t the case.
Aquariums, particularly saltwater tanks, require quite a bit of care and work.
Not Quite Done
Once you’ve set up your grouper tank (which itself can be quite a long process!), ensured it has properly cycled and added your fish, you might think that’s all there is to it.
However, you’ll need to conduct regular maintenance on your aquarium to keep it healthy.
Your groupers will need to be fed a well-balanced and nutritious diet that is packed with meaty foods.
Unlike some other marine fish species, groupers require primarily fresh or frozen seafood in their diet, so you can’t just offer them a few fish flakes and call it day.
Scallops, crayfish, halibut, and whole shrimp are some foods that you can feed them two times a day.
In addition to feeding your groupers, you’ll need to check their behavior every day and watch out for any signs of illness and disease.
Checking your aquarium equipment for signs of damage and testing your tank water are other tasks to complete regularly.
As you can see, keeping groupers isn’t always easy.
You’ll need to make sure you have the time to care for these fish to ensure they live long and happy lives.
Most groupers are relatively peaceful fish and can be housed in community tanks with and other grouper species.
That said, these fish are predators and will eat any fish or invertebrate that they can fit in their mouths.
If you want to keep a grouper in a community aquarium or reef tank, then you’ll need to choose their tankmates carefully.
Bear in mind that while these fish don’t actively provoke other fish, they are aggressive eaters and will prey on smaller fish and invertebrates (or anything that can fit inside their mouth!).
What Fish Can They Live With?
A large number of grouper species are known for their relatively docile temperament, so they can be housed with most species of fish of a similar size.
Avoid small fish and invertebrates as these will likely become snacks for your grouper.
Some tankmates that work well in a grouper tank include triggerfish (with caution), large marine angelfish, tangs, lionfish, and rabbitfish.
Make sure your tank is big enough to house other species of fish with your grouper.
Before introducing a grouper to a community tank, it’s best to rearrange the decor to break up any existing territories in the tank.
This is an important step if you have another grouper or aggressive fish already present in the tank, like triggerfish and marine angelfish.
Doing so removes established territories and puts all your fish in unfamiliar surroundings, which helps prevent any aggressive reactions towards your new grouper.
Best Time To Transfer
Additionally, introducing your grouper to your community tank in the evening when the lights have been off for a while can also reduce aggression.
A new grouper is usually rather timid at first and will hide away in caves or crevices.
Over time, as your grouper becomes more accustomed to its habitat, it will be more confident and come out more.
How Many Should You Keep Together?
Groupers can be kept alone, in pairs, or in groups.
However, if you want to keep more than one grouper in a tank, you’ll need to make sure you have an extremely large aquarium.
Most species need at least a 200-gallon or 250-gallon tank just for themselves and a handful of other fish.
Can I Keep Just One?
A grouper can live alone quite happily.
In fact, most groupers are kept alone in captivity as housing multiple ones together requires an incredibly big aquarium.
Groupers can develop illnesses or diseases that can affect their quality of life and lifespan.
In this section, I’ll be looking at some of the most common ailments that can affect grouper fish.
Signs of a Healthy Fish
A healthy grouper will have a strong appetite, bright eyes, good coloration, and generally be active around the aquarium.
Their tail and fins should look healthy and long without any tears or white edges.
They shouldn’t be exhibiting any antisocial behavior, such as laying at the base of the tank.
When groupers are stressed or sick, they will often look unwell and act abnormally.
Here are a few problem signs you should keep an eye out for.
- Cloudy eyes
- Lesions, cuts, or wounds on the body
- Missing scales
- Abnormal swimming pattern
- Clamped fins
- Loss of appetite
- Reddening, torn, or fraying fins/tail
- Respiratory distress
- Red gills
- Antisocial behavior
- Stringy white feces
Common Illnesses and Diseases
There are a few common illnesses and diseases that can affect saltwater fish and marine fish that you need to be aware of.
Identifying possible causes behind your grouper’s poor health is crucial for the right course of action and treatment.
Marine velvet is one of the most common diseases that can strike in saltwater fish.
If it isn’t dealt with quickly, it can swiftly spread to other fish.
The disease is caused by a dinoflagellate (which is a single-celled organism) known as Amyloodinium ocellatum.
This organism is naturally found in many tanks and is exceptionally resilient, making it hard to control.
Fish suffering from marine velvet will often have symptoms like bleeding or inflammation of the gills, difficulty breathing, lethargy, rubbing against tank objects, and destruction of lung tissue.
In severe cases, gold-colored spots will appear on your fish’s body, giving them a “velvet” appearance.
Unfortunately, by the time these golden spots appear, the gills are usually irreversibly damaged and treatment is no longer effective.
As marine velvet progresses, the gills and lung tissue will start to die off.
This can result in the fish gradually being unable to transport oxygen to the gill membranes, eventually leading to suffocation.
Sadly, this disease is often fatal in fish if not treated quickly.
Copper medications are exclusively used for marine velvet.
It is important to note that copper is lethal to fish in high doses, so make sure you follow the manufacturer’s instructions and dosage guidelines carefully.
Hole in the Head Disease
Hole in the Head Disease (also known as Lateral Line Erosion) is another disease that can affect saltwater fish and groupers.
It gets its name due to the pit-like holes it produces on the head of infected fish.
This disease’s symptoms include pits on the head, stringy white feces, subdued coloration, and appetite loss.
The exact cause of Hole in the Head Disease isn’t known, but it has been linked to poor water quality and nutritional deficiencies.
Sufferers of this disease usually have a deficiency in Vitamin D, Vitamin C, calcium, and phosphorus.
Irregular water changes can also influence the development of Hole in the Head Disease.
If left untreated, the disease will spread from the head along the lateral line.
Common treatment methods for this disease are proper nutrition and water changes. You should offer your fish live and frozen foods with vitamin supplements and fresh vegetables.
Improving the water quality in your aquarium is also mandatory for treating Hole in the Head Disease. It provides your fish with a healthy habitat so they can fully recover.
Vibrosis is an internal infection that is caused by Vibrio, a genus of gram-negative bacteria.
Fish can contract this disease through dead fish or contact with open sores.
When a fish contracts vibrosis, the disease progresses rapidly.
As it is an internal bacterial infection, many fish don’t show any external symptoms at first.
Signs usually only show up in the final stages of vibrosis.
At this point, the fish will usually display red streaks on the body (which often points to internal hemorrhaging), dark swollen lesions, cloudy eyes, red spots, lethargy, poor appetite, and respiratory distress.
The best treatment for vibrosis is oral antibiotics like kanamycin.
This medication should be administered in a quarantine or hospital tank as antibacterial medications can damage biological bacteria colonies in your filter.
It’s also important to note that vibrosis can be transmitted to humans by contacting infected fish, though this is quite rare. If you’re dealing with fish infected with this disease, make sure you avoid touching contaminated tank water and any cuts or lesions.
The breeding process for groupers varies between species, but many seem to spawn offshore on shelf and shelf-edge reefs.
Their pelagic larvae stay in the open ocean for around 40 to 60 days, at which point they will reach inshore nursery grounds.
The larvae turn into small juveniles and stay in the inshore nursery grounds for a fairly long period. Some species remain in the nursery habitat for 5 to 6 months, while others stay for 5 to 6 years.
After this period, they move offshore to join adult specimens.
As they move from environment to environment, each life stage of the juvenile groupers has different survival requirements.
Groupers are generally slow growers.
For example, male atlantic goliaths are considered mature once they are over 7 years old and are at least 45.5 inches long.
Females are considered mature when they are over 6 years old and are at least 48.2 inches long.
Atlantic Goliath Breeding
Spawning for Atlantic goliaths tends to happen during July, August, and September. It is linked to the lunar cycle.
They will form offshore aggregations of up to 100 or more fish.
Goliaths prefer to spawn in isolated patch reefs, shipwrecks, and rock ledges.
Females release eggs as males release sperm into the open offshore waters (known as broadcast spawning).
Upon fertilization, the eggs are pelagic and scattered by water currents.
Once the eggs hatch, the larvae are shaped like a kite, with the second dorsal-fin spine and pelvic fin spines extremely elongated.
After around 25 to 26 days after hatching, the pelagic larvae transform into benthic juveniles and are just 1-inch long.
In the 1980s, goliath spawning aggregations were particularly dismal (often containing fewer than 10 individuals) per site due to overfishing.
However, these fish now have legislative protection, so their spawning aggregation has greatly increased and risen to 20 to 40 fish per site.
Marine Betta Grouper Breeding
Interestingly, when marine betta groupers mate, they are often left with damaged fins and tails due to their rough spawning act.
The female lays up to 500 eggs on the roof of a cave or crevice.
After around 5 days, the eggs will hatch.
Fry have tiny yolk sacs when they are newly hatched, so they will begin to eat almost instantly.
These fish are slow growers and require at least 7 months to reach adult coloration.
As I mentioned earlier, most groupers are monandric protogynous hermaphrodites, which means they have the ability to change sex.
Groupers mature as females and can develop into males once they are sexually mature.
Can They Breed in Captivity?
Many groupers of species can be bred in captivity, though not a lot of information is available on how to breed them in home aquariums.
Groupers are incredibly hard to sex as there doesn’t appear to be any external differences between males and females.
If you want a unique and hardy centerpiece fish for your marine tank, then groupers are well worth considering.
There are a huge number of species, but not all of them belong in captivity.
Fortunately, a lot of the more colorful and vibrant species are suited to home aquariums.
Most varieties get to around 12 inches in length, which means they need a fairly big tank.
You’ll want to opt for at least a 200-gallon or 250-gallon tank for most species, though some will need larger aquariums.
These fish have huge appetites and heavy bioloads, so good filtration is key.
They are carnivores, so feed them a good variety of meaty foods such as scallops, whole shrimp, mussels, and squid every day.
Make sure you offer them whole food items once or twice a week, too.
As groupers are predatory fish, they should not be kept with small fish or invertebrates (basically anything they can fit inside their mouth).
However, they can be kept in community tanks with fish of a similar size.
As long as you have the time, space, and experience to keep a grouper fish, I think they’re a great species to add to a saltwater tank.
Not only are aquarium varieties striking in appearance, but they are also interesting to watch (especially when feeding!) and are a good fit for community aquariums that house large fish.