Betta imbellis Care Guide – Tank Setup, Feeding and Breeding

Quick summary

Betta imbellis is a moderately challenging, calmer alternative to the domestic betta, suited to keepers who can provide soft, acidic, warm water and a heavily planted 40+ litre tank. Its milder temperament even allows for pairs or small groups with careful setup, but beginners should be prepared for specific water chemistry needs and gentle filtration rather than a typical low-maintenance betta bowl.

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In this guide:

• Introduction
• Quick Stats
• Appearance
• Varieties and Morphs
• Natural Habitat
• Tank Size and Setup
• Water Parameters
• Filtration and Equipment
• Diet and Feeding
• Behaviour and Temperament
• Tank Mates
• Breeding
• Common Diseases
• FAQs

Introduction

Betta imbellis, widely known as the Peaceful Betta or Crescent Betta, is a wild betta species that offers aquarists a fascinating alternative to the ubiquitous domestic Betta splendens. Native to the lowland swamps and shallow waters of southern Thailand, peninsular Malaysia, and parts of Indonesia, this understated yet beautiful fish has earned its common name through a temperament that is genuinely milder than its domesticated cousin. While domestic bettas have been selectively bred for aggression over centuries of fighting culture, Betta imbellis retains a calmer disposition that, under the right conditions, allows it to be kept in pairs or even small groups – something unthinkable with most domestic betta males.

First described scientifically in 1975 by Ladiges, Betta imbellis has been known to the aquarium hobby for decades, though it remains far less common in the trade than Betta splendens. The species name “imbellis” is derived from Latin, meaning “peaceful” or “not warlike,” a fitting descriptor for a fish that would rather display than fight. Males possess a compact, elegant beauty, with iridescent blue-green scaling and a distinctive crescent-shaped caudal fin edged in red – markings that are subtle compared to the extravagant finnage of show bettas but no less captivating to the discerning fishkeeper.

It is worth noting that Betta imbellis is one of the parent species used in the creation of the increasingly popular Alien Betta hybrids, which are typically crosses between Betta imbellis and other wild betta species or domestic forms. These hybrids have generated enormous interest in the hobby, but purists rightly value the wild-type Betta imbellis for its own merits. Keeping and breeding pure Betta imbellis is a rewarding endeavour that connects the aquarist to the natural biodiversity of Southeast Asian freshwater ecosystems.

This care guide covers everything you need to know to keep Betta imbellis healthy and thriving in a home aquarium, from tank setup and water parameters to diet, breeding, and compatible tank mates.

Quick Stats

Scientific name	Betta imbellis
Common names	Peaceful Betta, Crescent Betta, Betta imbellis
Family	Osphronemidae
Origin	Southern Thailand, peninsular Malaysia, northern Sumatra (Indonesia)
Adult size	5-6 cm (2-2.4 inches)
Lifespan	3-5 years
Difficulty	Moderate
Breeding difficulty	Moderate
Temperature	22-28 °C
pH range	5.0-7.0
General hardness (GH)	2-10 dGH
Carbonate hardness (KH)	1-6 dKH
Minimum tank size	40 litres
Conservation status	Least Concern (IUCN)

Appearance

Betta imbellis is a small, compact labyrinth fish with a body shape that is noticeably more streamlined than domestic Betta splendens varieties. Adults typically reach 5 to 6 centimetres in total length, with a robust, slightly laterally compressed body. The overall impression is of an athletic, naturally proportioned fish – a stark contrast to the exaggerated finnage seen in halfmoon, crowntail, and other selectively bred domestic betta forms.

The most striking feature of Betta imbellis is the caudal (tail) fin, which is rounded and fan-shaped with a distinctive crescent or lunate marking. The tail is typically dark at the base, transitioning to iridescent blue or green with a bold red or orange crescent-shaped edge – the feature that gives the species its common name of Crescent Betta. This crescent marking is a reliable identification characteristic and is present in both wild-caught and captive-bred specimens.

Males in breeding condition display intense iridescent blue-green scaling across the body, particularly on the gill covers (opercula) and flanks. The scales shimmer with a metallic sheen that changes depending on the angle of light, creating a stunning effect in well-lit aquaria. The anal fin is elongated and pointed, edged in red, while the dorsal fin is relatively short and rounded. The pelvic fins are narrow and elongated, often tipped with white or red.

Females are considerably less colourful than males, displaying a brownish or olive-green body with faint horizontal barring. They may show some iridescent scaling, particularly when in good condition, but lack the vivid blues and reds of the males. Females also have shorter fins overall. The difference between the sexes becomes more pronounced as the fish mature, making sexing relatively straightforward in adults.

When stressed, frightened, or in poor conditions, both sexes will appear washed out and pale, with muted colouration. A healthy, confident male Betta imbellis in a well-maintained aquarium is a genuinely beautiful sight, with colours that rival many domestic betta varieties despite their more natural appearance.

Varieties and Morphs

Unlike domestic Betta splendens, which has been bred into dozens of fin types and colour varieties, Betta imbellis exists primarily in its wild-type form. However, there is natural variation between populations from different geographical locations, and selective breeding within the hobby has produced a few recognised colour variants.

Wild populations from different regions of southern Thailand, Malaysia, and Indonesia can vary in the intensity and hue of their iridescence. Some populations exhibit a more greenish sheen, while others lean towards a deeper blue or even turquoise. The extent and brightness of the red crescent on the caudal fin also varies between populations, with some displaying a broad, vivid red band and others showing a more subdued orange edging.

Captive breeding has produced some enhanced colour forms, including individuals with particularly intense blue colouration or expanded red markings. However, responsible breeders and hobbyists generally prioritise maintaining the natural appearance and genetic integrity of wild-type Betta imbellis rather than pushing for extreme colour variants. This is partly because hybridisation with Betta splendens or other closely related species can easily dilute the pure Betta imbellis lineage, and the hobby benefits most from preserving authentic wild-type stock.

It is important to mention the Alien Betta in this context. Alien Bettas are hybrids typically created by crossing Betta imbellis with other wild betta species, most commonly Betta stiktos or Betta smaragdina, and sometimes with domestic Betta splendens. These hybrids display extraordinary iridescent colouration that covers much of the body and fins, giving them an otherworldly appearance – hence the “Alien” name. While Alien Bettas are stunning fish, they are not Betta imbellis, and buyers should be careful to distinguish between pure Betta imbellis and hybrid fish when purchasing. Reputable sellers will clearly label their stock, and locality-specific wild-type Betta imbellis from known collection sites are generally the most valued by serious enthusiasts.

Natural Habitat

Betta imbellis is found across a relatively wide range in Southeast Asia, encompassing southern Thailand (particularly the provinces south of the Isthmus of Kra), peninsular Malaysia, and parts of northern Sumatra in Indonesia. The species has also been introduced to some areas outside its native range, including parts of Singapore. Within this distribution, populations can be found at low elevations, typically in coastal plains and lowland areas.

The natural habitats of Betta imbellis are characterised by shallow, slow-moving or still water bodies. These include rice paddies, roadside ditches, peat swamps, shallow marshes, and the margins of streams and ponds. The water in these environments is often heavily shaded by overhanging vegetation and may be stained dark brown by tannins leaching from decomposing plant matter – the classic “blackwater” conditions found across much of lowland Southeast Asia.

Water in these habitats is typically soft and acidic, with a pH that can range from 4.0 to 6.5 in peat swamp environments, though populations in rice paddies and ditches may experience slightly higher pH values. The water is warm, generally between 24 and 30 degrees Celsius, with minimal current. Dissolved oxygen levels can be low, which is why Betta imbellis, like all members of the genus, possesses a labyrinth organ that allows it to breathe atmospheric air directly from the surface.

The substrate in natural habitats is typically soft mud or decomposing leaf litter, and the water column is often choked with emergent and submerged vegetation. Floating plants are commonly present, providing cover and reducing light levels. This dense vegetation serves multiple purposes for the fish: it provides shelter from predators, creates territories for males, and offers surfaces for bubble nests. Understanding these natural conditions is key to replicating them successfully in the aquarium.

Betta imbellis shares its habitat with a variety of other small fish, invertebrates, and amphibians. In the wild, population densities can be surprisingly high in suitable microhabitats, with multiple males occupying territories in close proximity – a testament to the species’ relatively peaceful nature compared to domestic bettas.

Tank Size and Setup

While Betta imbellis is a small fish, it benefits from a thoughtfully designed aquarium that replicates the key features of its natural habitat. A minimum tank size of 40 litres is recommended for a single specimen or a pair. If you wish to keep a small group – for example, one male with two or three females, or even a carefully managed group with multiple males – a tank of 80 litres or more is strongly advised. The additional space allows males to establish territories and reduces the risk of aggression.

The tank should be set up with a focus on heavy planting and ample cover. Live plants are strongly preferred, both for aesthetic reasons and for their role in maintaining water quality and providing natural hiding spots. Excellent plant choices include Cryptocoryne species (which naturally co-occur with wild bettas in Southeast Asia), Java fern, Java moss, Anubias, and various floating plants such as Salvinia, Amazon frogbit, or water lettuce. Floating plants are particularly important as they dim the lighting, reduce stress, and provide a natural surface under which males will build bubble nests.

The substrate can be fine sand, aquatic soil, or a mix of both. A dark substrate is preferable, as it brings out the best colouration in the fish and more closely replicates their natural environment. Adding dried Indian almond leaves (Terminalia catappa), oak leaves, or other botanicals to the tank is highly recommended. These leaves release tannins that tint the water a natural amber colour, lower the pH slightly, and have mild antibacterial and antifungal properties. They also provide surfaces for biofilm growth, which the fish will pick at.

Driftwood, coconut shells, and small clay pots can serve as additional hiding spots and territorial markers. Arrange the hardscape and plants to create distinct visual barriers and separate territories within the tank – this is especially important if multiple males are being housed together. Line-of-sight breaks are critical for reducing tension between males.

A tight-fitting lid or cover glass is essential. Like all bettas, Betta imbellis breathes air from the surface and can jump. A gap between the water surface and the lid allows the fish to access atmospheric air while preventing escapes. The air above the water should be warm and humid, which a well-fitted lid naturally achieves. This is particularly important in cooler rooms, as cold air above the water surface can damage the labyrinth organ.

Lighting should be moderate to low. Betta imbellis comes from shaded environments and does not appreciate intense lighting. If you are growing plants that require stronger light, ensure that floating plants provide shaded areas where the fish can retreat.

Water Parameters

Betta imbellis thrives in soft, acidic water that replicates the conditions of its natural Southeast Asian habitat. While the species is reasonably adaptable, maintaining appropriate water parameters will result in the best colouration, health, and breeding behaviour. The following table summarises the ideal water parameters for this species.

Temperature	22-28 °C
pH	5.0-7.0
General hardness (GH)	2-10 dGH
Carbonate hardness (KH)	1-6 dKH
Ammonia	0 ppm
Nitrite	0 ppm
Nitrate	Below 20 ppm

The ideal temperature for Betta imbellis is between 24 and 27 degrees Celsius for everyday maintenance. Temperatures towards the upper end of the range can be used to condition fish for breeding. Avoid sustained temperatures above 30 degrees Celsius or below 22 degrees Celsius, as these extremes can cause stress and health issues.

A pH between 5.5 and 6.5 is ideal, particularly for breeding. The species can tolerate neutral pH (7.0) but will show its best colours and most natural behaviour in slightly acidic conditions. The use of Indian almond leaves, peat filtration, or commercially available blackwater extracts can help achieve and maintain a lower pH naturally.

Soft water is strongly preferred. In areas with hard tap water, mixing tap water with reverse osmosis (RO) or demineralised water can bring hardness down to appropriate levels. Regular water changes of 20-30% weekly are recommended to maintain good water quality, though the frequency and volume can be adjusted based on stocking levels and filtration capacity. Always ensure that replacement water is temperature-matched and dechlorinated before adding it to the tank.

Filtration and Equipment

Betta imbellis comes from still or very slow-moving water, so strong filtration currents should be avoided. A gentle sponge filter is the ideal choice for a Betta imbellis aquarium. Sponge filters provide effective biological filtration with minimal water movement, and they have the added benefit of not posing a risk to delicate fins or fry. An air-driven sponge filter connected to a small air pump with an adjustable valve allows you to control the flow rate precisely.

If you prefer to use a hang-on-back (HOB) filter or a small internal power filter, ensure that the outflow is baffled or redirected to minimise surface agitation and current. Betta imbellis is not a strong swimmer and will become stressed if forced to battle against a constant current. Many fishkeepers use filter sponges, spray bars, or baffle attachments to reduce flow from power filters.

A heater is generally necessary unless you live in a tropical climate where room temperature consistently stays within the species’ preferred range. An adjustable heater rated for the size of your tank is recommended. Place the heater near the filter outflow (if any) to ensure even heat distribution. A reliable aquarium thermometer should be used to monitor temperature – digital thermometers with external probes tend to be the most accurate.

Lighting should be appropriate for any live plants in the aquarium but not excessively bright. An LED light on a timer, providing 8 to 10 hours of light per day, works well. If the light is strong, floating plants will naturally shade the water column and create the dappled, low-light conditions that Betta imbellis prefers.

An air pump is useful even beyond powering a sponge filter, as gentle surface agitation helps with gas exchange. However, avoid creating strong bubbling or turbulence. Some fishkeepers choose to run their Betta imbellis tanks without any air-driven equipment at all, relying solely on the fish’s ability to breathe atmospheric air. While this can work in a well-planted, lightly stocked setup, some form of biological filtration is always advisable to maintain stable water quality.

Diet and Feeding

Betta imbellis is a micropredator in the wild, feeding on small invertebrates, insect larvae, zooplankton, and other tiny organisms found in and on the water surface. In the aquarium, this natural diet should be replicated as closely as possible with a varied menu of high-quality foods.

Live foods are the gold standard for Betta imbellis and will bring out the best colouration and breeding condition. Excellent live food options include mosquito larvae (a natural staple), Daphnia, baby brine shrimp (Artemia nauplii), Moina, micro worms, grindal worms, and wingless fruit flies. Culturing your own live foods at home is straightforward and ensures a parasite-free food supply.

Frozen foods are an excellent substitute when live foods are not available. Frozen bloodworm, frozen brine shrimp, frozen Daphnia, and frozen mosquito larvae are all readily accepted. Thaw frozen foods in a small amount of tank water before feeding to avoid temperature shock and to prevent uneaten frozen chunks from fouling the water.

High-quality micro pellets formulated for bettas or small carnivorous fish can form the base of the diet. Look for pellets with whole fish or insect meal as the primary ingredient, and avoid products with excessive fillers such as wheat or soy. Pellets should be small enough for the fish to consume easily. Many Betta imbellis will also accept high-quality flake food, though pellets and frozen or live foods are preferable.

Feed small amounts two to three times daily, offering only what the fish can consume within a few minutes. Betta imbellis has a small stomach and is prone to bloating and constipation if overfed. A varied diet that rotates between different food types throughout the week will ensure balanced nutrition and help prevent dietary deficiencies. Incorporating a fasting day once a week can also aid digestion.

Behaviour and Temperament

The most notable behavioural characteristic of Betta imbellis – and the feature that most clearly distinguishes it from domestic Betta splendens – is its comparatively peaceful disposition. While the species name “imbellis” literally translates to “peaceful” or “not warlike,” it is important to understand that this is a relative term. Male Betta imbellis will still display to one another, flare their gill covers, and defend territories. However, these interactions are far less likely to escalate to the damaging, sometimes lethal fights that are common with domestic male Betta splendens.

In a sufficiently large, well-planted aquarium with plenty of visual barriers, it is often possible to keep multiple male Betta imbellis together. This is one of the most appealing aspects of the species for many hobbyists. When males encounter each other, they will typically engage in lateral displays, flaring, and fin spreading. In most cases, the subordinate male will back down and retreat to his own territory without physical contact. Actual biting and fin damage can occur, particularly in cramped quarters or sparsely decorated tanks, so adequate space and cover are non-negotiable if you wish to keep multiple males.

Males are generally tolerant of females outside of breeding, though a female that is not ready to spawn may be chased away from a male’s territory. Keeping one male with two or three females in a well-planted tank is a popular and usually successful approach. This allows observers to witness natural social interactions and breeding behaviour without the risks associated with keeping multiple males.

Betta imbellis is a relatively shy species, especially when first introduced to a new aquarium. New fish may hide among plants and decor for several days before gaining confidence. A dimly lit, heavily planted tank will help them settle in more quickly. Once established, males will patrol their territories, display to rivals and potential mates, and build bubble nests under floating plants or overhanging leaves. They are curious fish that will often approach the front of the tank once they associate their keeper with food.

Like other labyrinth fish, Betta imbellis regularly visits the water surface to gulp air. This is normal behaviour and not a sign of distress. You will also observe them hunting for food among plants and on the substrate, flicking through leaf litter, and occasionally resting on broad leaves or other flat surfaces near the surface.

Tank Mates

Betta imbellis is one of the few betta species that can be successfully kept in a community setting, provided that tank mates are chosen carefully. The key principles are to select small, peaceful species that will not outcompete the betta for food, nip at its fins, or cause undue stress through boisterous activity. Tank mates should ideally prefer similar water conditions – soft, acidic, warm water with minimal current. Avoid large, aggressive, or highly active species that could intimidate this relatively shy fish.

Good tank mates

• Harlequin Rasbora – A peaceful, small schooling fish from the same Southeast Asian habitat that thrives in identical water conditions.
• Chili Rasbora – A tiny, non-competitive nano fish that is too small to bother Betta imbellis and shares a preference for soft, acidic water.
• Ember Tetra – A calm, diminutive tetra that occupies the mid-water column and poses no threat to bettas.
• Pygmy Corydoras – A bottom-dwelling species that stays small and will not compete with Betta imbellis for surface territory.
• Kuhli Loach – A peaceful, nocturnal bottom-dweller that largely avoids the areas of the tank that Betta imbellis frequents.
• Otocinclus – A gentle algae-eating catfish that minds its own business and helps keep the tank clean.
• Amano Shrimp – Large enough to avoid being eaten by Betta imbellis, these shrimp make excellent clean-up crew members.
• Celestial Pearl Danio – A small, peaceful species that does well in planted tanks and tolerates similar water parameters.

Fish to avoid

• Betta splendens (domestic) – Hybridisation risk and potential aggression make this an unsuitable companion for Betta imbellis.
• Tiger Barb – A notorious fin nipper that will harass and damage the fins of Betta imbellis.
• Serpae Tetra – Known for nippy behaviour, particularly towards slow-moving fish with visible fins.
• Chinese Algae Eater – Becomes aggressive and territorial as it matures and may attack Betta imbellis.
• Convict Cichlid – Far too aggressive and territorial for a peaceful Betta imbellis community.
• Paradise Fish – Another labyrinth fish that can be aggressive and territorial, leading to conflict.
• African Cichlids – Require completely different water chemistry and are far too aggressive for Betta imbellis.
• Giant Gourami – Grows far too large and will dominate or consume Betta imbellis.

Breeding

Breeding Betta imbellis is a highly rewarding experience and is considered moderately challenging. The species is a bubble-nester, meaning the male constructs a nest of air bubbles at the water surface, typically beneath a floating leaf or other overhanging structure. The breeding process follows a similar pattern to that of Betta splendens, though with some differences in intensity and aggression.

To condition a pair for breeding, feed them heavily with live and frozen foods for one to two weeks. Females ready to spawn will display a visibly rounded abdomen and may show vertical barring on their body – a sign of breeding readiness. Males will intensify their colouration and begin building a bubble nest.

A dedicated breeding tank of 20 to 40 litres is ideal. Set it up with a gentle sponge filter, a heater set to 26-28 degrees Celsius, and plenty of floating plants or a small piece of styrofoam to anchor the bubble nest. Indian almond leaves should be added to the water. The water level can be lowered to around 15 centimetres, which concentrates pheromones and makes it easier for fry to reach the surface to breathe. Provide hiding spots for the female, such as dense plant clusters or small caves.

Introduce the female to the breeding tank first, allowing her to settle for a day. Then add the male. The male will typically begin displaying to the female, flaring his fins and showing off his colours. He may chase the female initially, but the courtship of Betta imbellis is generally less aggressive than that of domestic Betta splendens. If the female is receptive, she will approach the male beneath the bubble nest.

Spawning involves the male wrapping his body around the female in a nuptial embrace beneath the bubble nest. During each embrace, the female releases a small number of eggs, which the male fertilises and then catches in his mouth, placing them carefully into the bubble nest. This process is repeated over several hours, with the pair producing anywhere from 50 to 200 or more eggs in a single spawning event.

After spawning, the female should be carefully removed from the breeding tank. The male will guard the nest, tending to the eggs by replacing fallen eggs into the nest and removing any that develop fungus. The eggs typically hatch within 24 to 48 hours, and the fry will become free-swimming two to three days after hatching. Once the fry are free-swimming, the male should also be removed to prevent him from eating them.

Free-swimming fry are very small and require infusoria, vinegar eels, or commercially available liquid fry food for the first few days. After about a week, they can graduate to freshly hatched baby brine shrimp (Artemia nauplii) and micro worms. Frequent small water changes with temperature-matched water are important to maintain water quality in the fry tank. Growth is steady, and young fish will begin to show colouration at around six to eight weeks of age. Males can typically be distinguished from females by three to four months of age.

Common Diseases

Betta imbellis is generally a hardy species when kept in appropriate conditions, but like all aquarium fish, it can be susceptible to a range of diseases, particularly when water quality is poor or the fish is stressed.

Velvet disease (Oodinium) is one of the most common ailments seen in wild-type bettas. It manifests as a fine, gold or rust-coloured dusting on the skin and fins, often most visible under a torch light. Affected fish may clamp their fins, rub against objects, and become lethargic. Treatment involves raising the temperature slightly, dimming the lights, and using a copper-based medication or a proprietary anti-parasitic treatment.

White spot disease (Ichthyophthirius multifiliis, commonly known as ich) is another frequent issue. It presents as small white spots resembling grains of salt on the body and fins. Treatment typically involves raising the temperature to 28-30 degrees Celsius and adding aquarium salt or a commercial ich medication. Early detection and treatment are key to a successful outcome.

Fin rot is a bacterial infection that causes the edges of the fins to become ragged, discoloured, and progressively eroded. It is almost always linked to poor water quality. Improving water conditions through regular water changes is often sufficient to halt and reverse mild cases. More severe infections may require antibiotic or antibacterial treatment.

Bloating and constipation can occur if the fish is overfed or given an unsuitable diet with too many dry foods and insufficient variety. Affected fish develop a visibly swollen abdomen. Fasting for one to two days and offering daphnia (which acts as a natural laxative) usually resolves the issue. In severe cases, bloating may indicate a swim bladder disorder or internal infection, which may require further investigation.

Columnaris (cotton wool disease) is a bacterial infection that can affect Betta imbellis, particularly in tanks with fluctuating temperatures or poor hygiene. It appears as white or greyish patches on the body, mouth, or fins. Treatment with antibacterial medications and improvement of water conditions is necessary.

Maintaining stable, clean water conditions, avoiding overfeeding, quarantining new fish before adding them to an established tank, and providing a varied diet are the best preventative measures against disease. A healthy, well-cared-for Betta imbellis has a strong immune system and is remarkably resilient.

FAQs

Can I keep multiple male Betta imbellis together?

Yes, it is possible to keep multiple males together in a sufficiently large, heavily planted aquarium with plenty of visual barriers. A tank of at least 80 litres is recommended for this purpose. Males will display to each other and establish territories, but serious aggression is uncommon if each male has adequate space and cover. Monitor the group closely, especially during the first few weeks, and be prepared to separate any individuals that show signs of excessive stress or aggression.

Is Betta imbellis the same as an Alien Betta?

No. While Betta imbellis is one of the parent species commonly used in creating Alien Betta hybrids, Alien Bettas are crossbreeds – typically between Betta imbellis and another wild betta species such as Betta stiktos or Betta smaragdina. Pure Betta imbellis and Alien Betta hybrids are distinct, and responsible sellers will label them accordingly. If you are interested in maintaining pure Betta imbellis, always purchase from reputable breeders who can confirm the lineage of their stock.

Can Betta imbellis live with domestic Betta splendens?

This is strongly discouraged. The two species can hybridise, which compromises the genetic integrity of Betta imbellis. Additionally, domestic Betta splendens males are typically far more aggressive than Betta imbellis males and may attack or kill them. Keeping the two species together also risks creating hybrid offspring that are difficult to identify and may be unknowingly distributed as pure Betta imbellis.

Do Betta imbellis need a heater?

In most climates, yes. Betta imbellis requires water temperatures between 22 and 28 degrees Celsius, with 24-27 degrees being ideal. Unless your home consistently maintains tropical temperatures year-round, an adjustable aquarium heater is necessary to keep the water within the appropriate range. Temperature fluctuations can stress the fish and make it more susceptible to disease.

How can I tell the difference between Betta imbellis and Betta splendens?