Glossary and FAQ

Betta Gillfriend care rules: one betta per tank. Mirror or flare practice: one 2-minute session a day, with at least 2 rest days a week. Train: up to 10 minutes a week.

Glossary

Term	Meaning
Acclimation	Slowly adjusting a fish to new water temperature and chemistry when moving it.
Ammonia (NH₃/NH₄⁺)	Toxic waste from fish and rotting food. Should always read 0.
Anabantoid	The group of fish with a labyrinth organ, including bettas and gouramis.
Aquatic vet	A veterinarian with training and experience in fish medicine. Find one at fishvets.org.
Beneficial bacteria / biofilter	Bacteria living in the filter and on surfaces that convert ammonia into nitrite, then nitrate.
Biopsy (gill or skin)	A tiny sample taken by a vet and examined under a microscope. Needed to confirm gill flukes and many parasites.
Bloat	A swollen belly, often from overfeeding or constipation.
Breeding bars	Vertical light bars on a female ready to spawn.
Bubble nest	A floating raft of bubbles built by males for eggs.
Caudal fin	The tail fin.
Caudal peduncle	The narrow part of the body just before the tail.
Chloramine	A disinfectant in some tap water, made of chlorine plus ammonia. Must be neutralised with a conditioner.
Clamped fins	Fins held tightly against the body; a general sign of illness or stress.
Columnaris	A fast-moving bacterial infection (Flavobacterium columnare), sometimes called "cottonmouth" or "saddleback".
Conditioning	Feeding and caring for fish to get them into peak breeding condition.
Culling	Choosing which fish to keep, rehome or humanely euthanise from a spawn.
Cycling	Growing beneficial bacteria in a tank before fish are added.
Dactylogyrus	An egg-laying gill fluke.
Dechlorinator / water conditioner	A product that neutralises chlorine and chloramine in tap water.
Dropsy	Fluid build-up causing swelling and "pinecone" scales; a sign of serious illness.
Fin rot	A bacterial infection that erodes the fins.
Flaring	A threat display: spreading fins and opening gill covers.
Flashing	Suddenly darting or rubbing against objects; often a sign of parasites or irritation.
Fry	Baby fish.
GH / KH	General hardness (minerals such as calcium and magnesium) and carbonate hardness (alkalinity, which buffers pH).
Gill covers (opercula)	The bony flaps covering the gills.
Gill flukes	Tiny parasitic flatworms (monogeneans) on the gills or skin. See Gill flukes.
Gravid	Carrying eggs (female).
Gyrodactylus	A live-bearing fluke, mainly on skin and fins.
Hospital tank	A separate tank for treating a sick fish.
Ich (white spot)	A parasite causing salt-grain white spots.
Jarring	Moving young males into individual containers so they don't fight.
Labyrinth organ	A special organ above the gills that lets bettas breathe air from the surface.
Lateral line	A sensory line along the fish's side that detects movement and vibration.
Monogeneans	The scientific group that includes gill and skin flukes.
Nitrate (NO₃⁻)	The end product of the nitrogen cycle. Less toxic, but kept low by water changes.
Nitrite (NO₂⁻)	A toxic middle product of the nitrogen cycle. Should always read 0.
Nitrogen cycle	The process by which bacteria convert ammonia into nitrite, then nitrate.
Oncomiracidium	The free-swimming larva of an egg-laying fluke.
Ovipositor	The small white egg tube on a female's belly.
pH	How acidic or alkaline water is. 7 is neutral.
Piping	Gulping at the surface constantly; a sign of breathing difficulty.
Plakat	A short-finned betta type.
Popeye	A bulging eye.
ppm / mg/L	Parts per million, or milligrams per litre. Essentially the same thing in water tests.
Praziquantel	A medicine aquatic vets commonly use against flukes and tapeworms.
Quarantine	Keeping new fish separate (at least 4 weeks) to watch for disease.
Shotgun treatment	Using several medicines at once without a diagnosis. Not recommended.
Sorority	A group of female bettas kept together. Risky.
Stress stripes	Horizontal stripes that appear when a betta is stressed.
Swim bladder	A gas-filled organ that controls buoyancy.
TAN	Total ammonia nitrogen, which is what most ammonia test kits measure.
Theront / tomont / trophont	The life stages of ich: free-swimming, cyst, and feeding on the fish.
VCPR	Veterinarian–client–patient relationship. In the US, it's needed for a vet to prescribe some fish drugs.
Velvet	A parasite causing fine gold or rust "dust" on the skin.

FAQ

Can a betta live in a bowl or a vase?

We don't recommend it. Welfare studies found bettas in small, bare containers swim less and show more abnormal behaviour. The University of Illinois vet hospital says bettas shouldn't be kept in bowls, and that they can't live off plant roots. We recommend at least 5 gallons (about 19 L), heated, filtered and furnished, with 10+ gallons for giants. See Tank setup.

What temperature should my betta's water be?

76–81°F (about 24–27°C), kept steady with a heater and checked daily with a thermometer.

Does my betta need a filter?

Yes. A filter is home to the beneficial bacteria that break down ammonia. Choose a gentle one, such as a sponge filter or a filter with adjustable flow.

How often should I change the water?

In a cycled tank, 10–25% weekly, with a gravel vacuum. Always use a dechlorinator and match the temperature. See Water quality.

How much should I feed?

A small amount your betta finishes in about 2 minutes, once or twice a day, with an optional fast day once a week. Watch the belly and adjust. See Diet and feeding.

My betta isn't eating. What should I do?

Test the water and temperature first. New bettas often skip a day or two while settling. If your betta hasn't eaten for more than 2–3 days, or shows other signs (clamped fins, fast breathing, spots), check the symptom lookup table and contact an aquatic vet.

Why is my betta lying at the bottom?

Bettas rest a lot, especially at night, after meals, and as they age. But constant lying on the bottom can mean cold water, poor water quality, or illness. Check temperature and water first. See Lethargy.

My betta made a bubble nest. Does he want a mate?

No. A nest simply means he's mature and comfortable. And no nest is fine too.

Is it OK to use a mirror?

We recommend a cautious approach: one 2-minute session a day, with at least 2 rest days a week, and never leave a mirror in the tank. See Enrichment and flare training.

Is the app's flare mode safe?

The same rules as a mirror apply. Research shows bettas react to on-screen bettas much like real ones, including a rise in stress hormones, so keep sessions short, with rest days, and stop at any sign of stress.

Can two bettas live together?

Never two males. A male and female shouldn't live together long-term. See Tank mates.

What fish can live with my betta?

Often none is best. If you'd like company, snails, and in larger tanks (40+ L / 10+ gallons) peaceful species like corydoras and otocinclus, can work. Avoid fin nippers, gouramis and colourful, long-finned fish. Quarantine every newcomer.

How long do bettas live?

Usually 3–5 years with good care (PetMD). No study shows tail type or colour changing that; see Do tail type, colour or size change lifespan? and Old age.

Why is my koi betta changing colour?

Koi and marble patterns are controlled by many genes and often change over the fish's lifetime. Gradual change in an active, eating fish is normal. Sudden dullness, or white, grey or gold film, isn't. Check for illness.

What are the white or horizontal stripes on my betta?

Horizontal stress stripes often appear when a betta is new, stressed or unwell. Vertical breeding bars on a female mean she's ready to spawn. See Behaviour and body language.

My betta's fins are getting shorter. Fin rot or biting?

Fin rot usually shows ragged, discoloured, gradually receding edges. Fin biting usually shows clean chunks missing, often overnight. Both improve with clean water and a calm tank. See Fin rot and Fin biting.

Should I add aquarium salt?

Not routinely. Salt has specific uses (for example, some treatments for ich, and protecting fish against nitrite poisoning), but it's not a cure-all, and it doesn't reliably work against gill flukes. Use it only with guidance from an aquatic vet. More in Myths and facts.

Should I use Indian almond leaves?

They're a nice optional extra: they tint the water, give your betta something to rest on, and some small studies suggest benefits. But they can lower pH, so test your water. They're not a medicine.

I lost a betta to gill flukes. What should I do before getting another?

We're so sorry. Flukes are one of the hardest betta illnesses to spot and treat, and losing a fish to them isn't a sign you did something wrong. Before adding a new fish: reset or thoroughly disinfect the tank and equipment, re-cycle it, and quarantine your next betta for at least 4 weeks, ideally with an aquatic vet's input on a preventive check or treatment. See After losing a fish to flukes.

How do I find an aquatic vet?

Try the American Association of Fish Veterinarians' "Find a Fish Vet" map (fishvets.org) or WAVMA's directory. Many exotic-animal vets also see fish, and some offer remote consultations.

Can I get sick from my fish tank?

It's uncommon, but possible. Some fish bacteria (notably Mycobacterium) can infect people through cuts. Wear gloves if you have cuts or a weakened immune system, never siphon by mouth, and wash your hands after tank maintenance (OATA, Merck).

Sources

Care guide by Betta Gillfriend (Bespok Labs, BC, Canada). It is general information, not vet advice. If your betta is sick, ask an aquatic vet.