Halfmoon Male Betta Mix (Betta splendens)

Halfmoon Male Betta Mix at a glance

The Halfmoon Male Betta Mix is a single domestic male Siamese fighting fish, Betta splendens, from long-finned halfmoon lines. The word “mix” is about colour: the fish is not picked to match a particular colour or pattern, so the male you receive will carry his own markings rather than copy any fish in the photographs. One purchase supplies one live fish.

Before anything else, he needs a home of his own. Plan a heated, filtered and covered aquarium of at least 20 litres, furnished with plants or other cover, with gentle water movement and clear access to the surface. Get that set-up running and fully cycled before you order; it matters far more to his welfare than any colour or fin detail.

A halfmoon male is a showpiece rather than a community fish. He is at his best alone, in a calm, planted tank where strong flow does not push his fins about and no tank mate is tempted to nip them.

Quick facts

What halfmoon and mix mean

Halfmoon is a trade name for long-finned domestic Bettas bred for a broad tail that opens towards a half-circle when the male displays. It describes fin shape, not a separate species: every halfmoon is Betta splendens Regan, 1910, the fish sold as the Betta or Siamese fighting fish and recorded in the Osphronemidae family by NCBI Taxonomy. The scientific name is the reliable identity; colour and tail names are breeders’ labels.

Seriously Fish notes that the species has been extensively line-bred for vigour and the ornamental trade, and has been hybridised with close relatives. A genome-wide study of domestic Bettas by Kwon and colleagues in 2022 mapped the genetics behind their variety of colour, fin shape, body size and behaviour. For a buyer, the practical point is simple: a photograph shows colour and fin shape, but it cannot show a fish’s age, health or temperament.

The wild species comes from central Thailand and the lower Mekong basin, where it lives in standing or slow water: floodplains, canals, rice paddies and medium to large rivers. The wild form is rarely kept, and wild Betta splendens is assessed as Vulnerable by the IUCN. That status describes wild populations; it is not a label for a domestic halfmoon male.

What “mix” means when you order

This listing is a colour mix. The male is not selected to match a photograph, so expect any of the colours and patterns these lines produce. The photographs show the halfmoon fin shape and the kind of colour the lines can carry. Gallery images have been digitally enhanced to improve image quality. Natural colour, pattern, size and maturity can vary between live animals.

Sex is guaranteed only when the exact product or selected option explicitly states male or female. This Halfmoon Male Betta Mix listing is sold as male.

For deeper background, our Betta fish care guide covers the species in more detail, and the betta collection shows the other fin types and colour lines in the range if you are still comparing.

Setting up his aquarium

Plan everything around one male living on his own. OATA’s UK care sheet for Bettas recommends at least 20 litres for a single male, and Tropical Fish Co uses the same figure as its minimum starting point. Seriously Fish suggests a base of 45 × 30 cm, roughly 41 litres, for a single male or a pair, and does not support keeping the species in tiny aquaria or jars. Treat 20 litres as the floor and the bigger footprint as a comfortable aim: more water holds temperature and water quality steadier, and it gives a long-finned fish more places to rest.

Two behavioural studies published in 2024 add useful detail. In one, males kept in a furnished 19.3-litre tank showed more activity and fewer abnormal behaviours than in smaller or bare containers; in the other, small bowls restricted normal swimming and physical enrichment mattered. Neither makes 20 litres an ideal ceiling, but both point firmly away from bowls and bare tanks.

Equipment to have running first

• Filter: matured before he arrives and set for gentle movement. Seriously Fish suggests an air-powered sponge filter, because the species naturally lives in sluggish water.
• Heater: a thermostatic heater, needed all year round for a Betta in a UK home.
• Thermometer: a separate one, so you read the water itself rather than trusting the heater setting.
• Lid: a secure cover with a small air gap above the water.
• Test kits: for ammonia, nitrite, nitrate, pH and hardness.
• Maintenance kit: tap-water conditioner, a gravel siphon and a bucket used only for the aquarium.

Cycle the filter before you order

A new aquarium is not ready just because the water looks clear. Its filter needs time and a source of ammonia to build up the bacteria that turn toxic ammonia into nitrite, which is also toxic, and then into the safer nitrate. The RSPCA’s aquarium guidance recommends fishless cycling and adding fish only after ammonia and nitrite have risen and fallen back to zero. Record your test results; if either reading is above zero, the tank is not ready for him yet. Our guide to setting up a first tropical tank walks through the process step by step.

Flow, surface access and the lid

Bettas have a labyrinth organ that lets them breathe air at the surface, and they must be able to reach it at all times. OATA is clear that this ability does not reduce the need for a proper aquarium with adequate filtration. Keep the current gentle, leave a small air space under the cover and make sure floating plants never seal the whole surface. The lid matters too: it cuts the risk of a jump.

Watch how he copes once the tank is running. Very long fins can change how an individual deals with flow, so if he is repeatedly pushed off course or struggles to rest, reduce or spread the outflow without switching off the filter’s biological work.

Plants, shade and safe decor

Seriously Fish describes this species at its best in a well-planted, shady aquarium with plenty of surface cover. Useful choices include:

• floating plants such as Salvinia or Riccia, or tropical lilies (Nymphaea);
• tall stem plants and Cryptocoryne;
• driftwood carrying Microsorum or Taxiphyllum;
• small clay pots or short lengths of pipe as extra shelter;
• dried leaf litter, which adds cover and releases tannins.

Whatever you choose, check it with his fins in mind. Avoid sharp edges, rough openings that could trap his body and decor that blocks the surface. In the 2024 study that compared the same 19.3-litre tank furnished and bare, the bare version produced more hovering, repetitive swimming and interaction with the glass, which is a good reason to give him real structure rather than an empty box.

Water quality and temperature

Tank-reared Bettas are usually undemanding about water chemistry, according to OATA’s Betta care sheet. What matters most is clean, stable water, so use the figures below as ranges to hold steady rather than numbers to chase.

Why we suggest 26–28°C

The published ranges come from different settings. OATA’s 20–28°C covers tank-reared Bettas in aquaria, Seriously Fish gives 22–30°C for the species in the aquarium, and FishBase records 24–30°C for the tropical waters where it lives wild. Tropical Fish Co settles on 26–28°C as a stable working target for a domestic male because it sits inside all three.

Measure with a separate thermometer and read it regularly. If a reading drifts, check the heater and thermometer before changing anything, then correct the temperature gradually rather than with a sudden swing.

Choose the heater by the maker’s guidance on aquarium volume, installation, minimum water depth and room temperature rather than a universal watts-per-litre slogan, then confirm the result in the water with your thermometer.

Wild fish and domestic fish differ

Seriously Fish notes that wild-collected Bettas are likely to prefer pH 5.0–7.0, while ornamental strains are unfussy across pH 6.0–8.0. Your halfmoon male is an ornamental fish, so there is no need to acidify or soften water that already sits in that range. Do not adjust pH or hardness simply to hit the middle of a published range; steady water matters more than an exact decimal.

UK tap water

Tap water is not one chemistry across the UK: hardness varies with local geology and supply. Treat every fill and water change with conditioner to remove chlorine or chloramine, and test again after any domestic softener or filter. Our aquarium water parameters guide explains what each test tells you, and the water parameter matcher lets you compare your own readings with the ranges above.

Feeding a long-finned male

In the wild, Betta splendens feeds on zooplankton, mosquito larvae and other insect larvae, according to FishBase, and Seriously Fish adds aquatic and terrestrial invertebrates. In the aquarium, a halfmoon male does well on prepared food as long as it is good quality and carefully portioned.

Building his diet

• Base food: a good-quality flake or pellet. OATA notes that specialised Betta pellets are made with these fish in mind.
• Variety: small frozen or live foods such as daphnia, Artemia (brine shrimp) or small bloodworm. Seriously Fish recommends offering these regularly for the best colour and condition.
• Occasional extras: small insects such as pinhead crickets or Drosophila fruit flies, which Seriously Fish suggests feeding on fish flakes or vegetable matter first.

How much and how often

OATA advises feeding Bettas only what they can eat within a few minutes, once a day. Seriously Fish warns that Bettas seem particularly prone to obesity, so err on the small side and remove anything left uneaten before it breaks down and fouls the water.

Skip rules of thumb such as matching a portion to the size of his eye, a fixed pellet count for every brand or a compulsory weekly fast. Pellet size and energy vary between foods, and his appetite changes with age, condition and water temperature. Follow the food maker’s guidance, watch his body shape and adjust. If more than one person feeds the tank, pre-measure the portions so he is not fed twice by mistake.

A newly arrived fish may ignore dried food at first. Seriously Fish notes that captive Bettas normally accept dried products once they recognise them as food, so offer small amounts and be patient rather than adding more.

When you are away

Arrange a competent carer with pre-measured feeds and written instructions, and make sure they know how to spot a heater or filter problem. If you plan to use an automatic feeder, test it well before you travel rather than trusting it for the first time after you leave.

A readiness check before you order

UK law expects more than a fish that merely survives. The Animal Welfare Act 2006 protects vertebrates, including fish, and the keeper’s duty covers a suitable environment and diet, the chance to behave normally, appropriate social housing and protection from pain, injury, suffering and disease. For one halfmoon male, that duty turns into a short checklist. Work through it before you order, not while the parcel is on its way.

• The aquarium holds at least 20 litres of actual water once substrate and decor are in, not just on the box label.
• The filter has finished fishless cycling, and ammonia and nitrite both test at zero.
• The heater and a separate thermometer hold your planned temperature steadily.
• Flow is gentle and the surface stays open for him to breathe.
• The lid fits securely, with a small air gap beneath it.
• Plants and decor give cover without sharp edges or gaps that could trap him.
• He will live alone, and you have a plan for separating him if you ever try a companion.
• Food, conditioner, test kits, a siphon and aquarium-only buckets are ready.
• Someone can look after the tank if you travel.

A nominal 20-litre kit is a common trap: check its internal dimensions and real filled volume, because decor takes up water and a bare, unstable container is not the same as a mature, furnished aquarium of the same size. When every point is ticked, you are ready to order. If one is still open, wait until it is; a settled, stable aquarium is the best welcome a new fish can have.

Arrival day and his first weeks

Every order is hand-packed by the Tropical Fish Co team: bagged in pure oxygen, packed in an insulated poly box and given a heat pack when the weather calls for it. A licensed live-animal courier carries the parcel, and you receive an email with the tracking number and your confirmed delivery date. Live fish cannot be left unattended, so someone must be at the address to receive him. The full terms are on our delivery and Live Arrival Guarantee page.

On the day

1. Be at the delivery address on the confirmed day; the Live Arrival Guarantee requires someone there to receive the parcel.
2. Before the parcel is opened, start one continuous unboxing video with the sealed parcel and outer box in view, keep filming as you open it, and show the fish still inside the sealed bag. Film every parcel this way: the store needs this video with any Live Arrival Guarantee claim.
3. Open and inspect the parcel on the day it arrives.
4. Float the sealed bag in his aquarium for 20–30 minutes before releasing him.
5. Release him into the aquarium without pouring the bag water into your tank.
6. If anything has gone wrong, get in touch the same day, by WhatsApp for the fastest reply, with your order number and the unboxing video, and a replacement or refund will be arranged.

The first days and weeks

Give him time to settle and keep the routine simple. Offer a small meal and remove whatever he leaves. Watch his breathing, appetite, fins and swimming, and compare what you see with the signs of a healthy fish that OATA lists: clear, bright eyes, undamaged fins, intact scales, no ulcers or bumps and normal swimming.

Keep testing for ammonia and nitrite over the first weeks. Adding a fish and starting to feed raises the waste the filter must handle, and OATA explains that the filter’s bacteria need time to catch up whenever stocking or feeding increases. Too much, too soon can cause “new tank syndrome”, with ammonia and nitrite climbing to harmful levels. One fish in a properly cycled tank is a light load, but a test kit is the only way to be sure.

Weekly routine and health checks

Good husbandry is the best protection a Betta has. OATA notes that Bettas can be stressed by even the smallest amounts of ammonia and nitrite, so a steady weekly routine does more for him than any bottle on the shelf.

Every week

• Make a partial water change of 25% at least once every week, as OATA strongly recommends, siphoning solid waste from the gravel as you go.
• Test the water at least once a week so ammonia and nitrite cannot build up unnoticed, and log nitrate, pH and hardness alongside.
• Treat all replacement water with a tap-water conditioner to remove chlorine or chloramine.
• Check the filter for blockages. If the media needs cleaning, rinse it lightly in the tank water you have just removed; do not run it under the tap, because chlorine or chloramine can kill the beneficial bacteria.
• Compare the thermometer reading with your target and make sure the heater is working.

Changes to watch for

Every fish varies a little, but OATA suggests watching for changes in:

• swimming: hanging at the surface, sitting on the bottom or swimming erratically;
• colour: turning darker or paler than usual;
• temperament: more or less aggression, or hiding more than normal;
• breathing: gill covers moving faster or slower than normal;
• appearance: white spots, fluffy growths, or loss of fins or scales;
• condition: gaining or losing weight;
• feeding: eating less or losing interest in food.

A Betta rising briefly to take a gulp of air is normal for a labyrinth fish. What matters is a change from his own usual pattern.

If something looks wrong

1. Confirm the temperature and test ammonia, nitrite, nitrate and pH.
2. Think back over recent additions, maintenance, feeding and equipment changes.
3. Compare his breathing, posture, appetite and fins with his normal behaviour.
4. Avoid combining medicines or raising the temperature on the strength of an internet diagnosis.
5. Seek experienced help if signs are severe, persistent or unexplained; OATA’s find a fish vet directory helps you locate fish-health help in the UK.

A torn fin, a white mark, a swollen belly or odd swimming can each have more than one cause. The MSD Veterinary Manual puts aquarium history and water analysis at the heart of diagnosis, which is why correcting water quality comes first, even though it cannot name the cause on its own.

Behaviour, bubble nests and breeding

A male Betta is a solitary, territorial fish with plenty of individual character. FishBase describes the species as a facultative air-breather and bubble-nest builder, and notes plainly that males will fight each other. Its common name comes from the tradition of keeping males to fight one another in organised bouts, which is exactly why two males must never share a tank.

Display and temperament

Expect him to display, spreading his fins at anything he treats as a rival. Keep neighbouring Betta tanks out of each other’s direct view. Temperament varies from one male to the next, so learn your own fish’s habits rather than relying on a general rule.

Bubble nests

Bubble nests are part of reproductive behaviour, and a male may build one with no female present. A nest does not prove he is healthy, and the absence of one does not mean something is wrong. Judge his welfare on water tests, feeding, breathing, posture and change over time.

Breeding is a separate project

This listing supplies a single male for a home aquarium, and breeding needs a female, a separate set-up and a plan for the young. For readers who want to understand what is involved:

• FishBase notes that the sexes should be kept apart except for mating, with only one female introduced to a breeding tank of about 20–30 litres.
• The male builds a floating nest of bubbles, often beneath a broad leaf or among fine surface plants, and does not usually tolerate the female nearby until it is finished.
• Seriously Fish stresses plenty of cover for the female and the tightest-fitting cover possible over the tank, because fry need a layer of warm, humid air for their labyrinth organ to develop properly.
• A female ready to spawn turns paler and shows dark bars on her flanks, and spawning takes place beneath the nest.

Treat breeding as a planned project with its own research, not a side effect of keeping one male.

Tank mates and living arrangements

The safest plan for a halfmoon male is an aquarium of his own. Seriously Fish does not recommend the species for the standard community aquarium and says it is best kept alone; an individual sometimes tolerates other species, but that is the exception rather than the norm. Ornamental strains, it adds, seem more aggressive than any other Betta species.

Other male Bettas

Never keep two males together. OATA warns that they will fight until one is severely injured or, more likely, killed, and the RSPCA’s guidance on keeping fish together also recognises that male Bettas fight their own kind. In published experiments, extra space and furnishings did not make it safe to house males together.

Female Bettas

Seriously Fish describes the usual practice as keeping males and females apart unless breeding, and FishBase says the same. OATA mentions keeping a male with at least five females in a densely planted aquarium that breaks up the line of sight, but says inexperienced keepers should not attempt it, and it recommends at least 60 litres for a group of females. For almost every home aquarium, a single male on his own is the right choice.

Other kinds of fish

OATA points out that male Bettas are not aggressive towards other species of fish but are often the target of intense fin nipping, which can cause stress, disease and death. Seriously Fish also warns against fish with a similar body shape or trailing fins, which a male may treat as rivals.

If you still want a companion, Seriously Fish notes that some small cyprinids and loaches from similar still-water habitats can work, provided you research them properly before buying. Screen any candidate for adult size, water needs, activity, fin nipping, competition at feeding time and the space the whole group needs, and have a separation plan, such as a spare heated tank, ready before you try.

Shrimp, snails and fry

Treat small invertebrates and fry as uncertain companions. A Betta may investigate or hunt smaller animals, while some larger or defensive invertebrates bring their own injury risk. They are not a cleaning crew, and they are not live food to add on the off chance.

Questions keepers ask

How big does a Halfmoon Male Betta Mix get?

Adults reach about 7 cm in body length. OATA gives about 7 cm for Bettas, Seriously Fish records 70 mm standard length and FishBase 6.5 cm total length. His long fins make him look noticeably larger than his body.

What size aquarium does a Halfmoon Male Betta Mix need?

At least 20 litres for one male, which is OATA's recommendation and our own minimum, with a heater, a matured filter, a secure lid and plenty of cover. Seriously Fish suggests a 45 × 30 cm base, roughly 41 litres, and more water is easier to keep stable.

Can two Betta splendens males share a tank?

No. Keep one male per aquarium, because two males will fight until one is severely injured or killed. Males and females are also normally kept apart unless you are breeding them.

Is the Halfmoon Male Betta Mix suitable for beginners?

Yes, for a careful beginner whose aquarium has already cycled. The heater, matured filter, test kits and a gentle-flow layout need to be in place before he arrives; surviving in a bowl is not the same as good care.

What should I feed a male Betta?

A good-quality flake or Betta pellet as the base, with small frozen or live foods such as daphnia, Artemia or bloodworm for variety. Give only what he eats within a few minutes, once a day, because Bettas are prone to obesity.

What temperature and pH does Betta splendens need?

Aim for a steady 26–28°C, our practical target inside OATA's broad 20–28°C guidance for tank-reared Bettas, with pH 6–8 and 4–12 dGH. A thermostatic heater is needed all year round in UK homes.

Is a male Betta aggressive, and does he nip fins?

He will fight another male Betta and may treat long-finned or similarly shaped fish as rivals. With other species he is more often the target than the attacker: OATA notes that male Bettas often suffer intense fin nipping.

What can live with a Halfmoon Male Betta Mix?

He is safest alone. If you want a companion, consider only small, calm cyprinids or loaches from similar still-water habitats, after careful research and with a separation plan ready. Avoid fin nippers, boisterous fish, other Bettas and long-finned fish; shrimp and snails are uncertain companions.

How does a Halfmoon Male Betta Mix arrive alive in the UK?

He is hand-packed in a bag of pure oxygen inside an insulated box, with a heat pack when the weather calls for it, and carried by a licensed live-animal courier. Someone must be in to receive him. Film one continuous unboxing video from the sealed parcel to the fish still in his bag, then float the bag for 20–30 minutes before release. For a Live Arrival Guarantee claim, send the video and your order number the same day.

Sources and further reading

The care advice on this page draws on these public sources. Each is worth reading in full if you want the detail behind a recommendation.

• FishBase: Betta splendens species summary: classification, wild habitat, diet and recorded maximum length.
• Seriously Fish: Betta splendens species profile: aquarium size, water, diet, behaviour and breeding.
• OATA: How to look after Siamese fighting fish (Bettas): the UK trade body’s care sheet for water values, tank size, feeding, maintenance and compatibility.
• RSPCA: choosing an aquarium for pet fish: filtration, cycling and welfare basics.
• RSPCA: keeping pet fish together: compatibility, including fighting between male Bettas.
• NCBI Taxonomy: Betta splendens Regan, 1910: accepted scientific name and family.
• Kwon et al. (2022), The genetic architecture of phenotypic diversity in the Betta fish: genetics of domestic colour, fin and body variation.
• MSD Veterinary Manual: management of aquarium fish: water-quality-led investigation and diagnosis.
• OATA: find a fish vet: locating fish-health help in the UK.

Our own Betta fish care guide and delivery policy, both linked earlier on this page, set out the house targets and Live Arrival Guarantee terms used here.