What are the different types of guppy tails?

The main tail types are veiltail, delta, fantail, lyretail, double sword, flag, spearhead, pintail and roundtail. Tail shape is separate from strain, which describes colour and pattern.

What is the most popular guppy strain?

Cobra, mosaic, tuxedo, koi and moscow are among the most widely kept. Strain names describe pattern and colour, and any of them can appear on several different tail shapes.

Do guppy tail types affect care?

Yes. Heavily finned strains are weaker swimmers, need gentler flow, and are more prone to fin damage and rot. Shorter-finned and wild-type guppies are consistently hardier.

Can you mix guppy strains?

You can, but the offspring will not breed true and colour patterns disperse within a couple of generations. Keep one strain per tank if you want to maintain it, or keep males only where mixing does not matter.

Guppy tail types and colour strains

Wild guppies are small, grey-bodied fish with a modest tail and a scatter of iridescent spots on the flank. Everything in a shop tank labelled "fancy guppy" is the result of roughly a century of selective breeding away from that starting point.

Knowing the vocabulary is useful for two reasons beyond the obvious. It tells you what you are actually buying, since "assorted fancy guppy" covers a range of quite different fish. And fin type has real husbandry consequences — some of these strains are meaningfully harder to keep than others.

Common nameGuppy

Water TypeFreshwater

Key checksfin length vs swimming ability · strain purity · nipping risk

ApproachShorter-finned strains are hardier; long-finned strains need calmer tanks

Tail shapes

Guppy tails are classified by the outline of the caudal fin. Show standards (the IFGA in the US, similar bodies in Europe and Asia) define these precisely; shop fish are looser approximations.

Male fancy guppy with a wide delta triangle tail fin — Delta / triangle tail

Delta / triangle tail. The dominant fancy shape — a large fin opening to a wide triangle, ideally at around a 70° spread. Most "fancy guppies" are deltas.

Male fancy guppy with a narrow trailing veiltail — Veiltail

Veiltail. Similar size to a delta but with a narrower spread, hanging in a more rectangular, trailing shape. Flows dramatically; the fin is heavy.

Male fancy guppy with a broad rounded fantail — Fantail

Fantail. Between the two — a broad fan, slightly rounded at the trailing edge.

Male guppy with a short round spadetail close to wild type — Round / spadetail

Round tail / spadetail. A short, rounded or spade-shaped fin, much closer to the wild form. Increasingly popular among people who want guppies that swim properly.

Male fancy guppy with lyretail U-shaped ray extensions — Lyretail

Lyretail. The top and bottom rays extend well beyond the body of the fin, producing a distinctive open "U" with two long points.

Male fancy guppy with double sword tail extensions — Double sword

Double sword. Extensions from both the top and bottom edges, with the centre of the fin shorter — an elegant, symmetrical shape. Top sword and bottom sword have the extension on one edge only.

Male fancy guppy with a single central pintail needle point — Pintail / needle tail

Pintail / needle tail. A single fine point extending from the centre.

Male guppy with a short squared flag tail — Flag tail

Flag tail. A short, squared-off rectangular fin.

Male guppy with a small pointed spearhead tail close to wild type — Spearhead / cofertail

Spearhead / cofertail. Small, pointed, close to wild-type.

Fin length has consequences

This is the part that matters for care rather than aesthetics.

A delta or veiltail male is carrying a fin substantially larger than his body, and he is dragging it through the water every second of his life. Compared with a round-tailed or sword-tailed fish, he is:

A weaker swimmer, and more affected by flow. Strong filter output that a wild-type guppy ignores will leave a veiltail male permanently struggling behind the hardscape.
More prone to fin rot, simply because there is far more fin tissue, and damage takes longer to heal.
A much more attractive target for fin-nippers. This is the main reason bettas and long-finned guppies are a poor mix, and why tiger barbs and serpae tetras are a firm no.
More vulnerable to unguarded intakes. Trailing fins get pulled into filter inlets that a shorter-finned fish would swim past.

If you want guppies that behave more like the fish in the wild — fast, agile, constantly active — look for short-finned strains, or Endler's livebearers, which have never been bred for long fins at all.

Colour strains and patterns

Colour is described separately from tail shape, so a fish is typically both — a "blue delta cobra", for example.

Guppy with cobra snakeskin reticulated pattern on body and fin — Cobra / snakeskin

Cobra / snakeskin. Fine rosette or chain-link patterning over the body and often into the fin. Snakeskin refers to the tightest, most regular version of the pattern.

Guppy with tuxedo dark rear half and pale front — Tuxedo

Tuxedo. The rear half of the body is a solid dark block — usually black or deep blue — contrasting sharply with a paler front half.

Guppy with irregular mosaic patches in the tail fin — Mosaic

Mosaic. Irregular, interlocking patches of colour in the tail, without the regularity of a cobra pattern.

Guppy tail with fine dark grass-like speckling — Grass

Grass. Very fine dark speckling across the tail, like scattered seed.

Guppy tail with delicate lace net pattern on pale ground — Lace

Lace. A delicate net-like pattern, generally on a paler ground.

Guppy with metallic platinum sheen on head and front body — Metal / platinum

Metal / platinum. A solid metallic sheen over the head and front body, usually silver, gold or platinum.

Solid Moscow blue guppy with uniform body colour — Moscow blue

Moscow. Intense solid colour covering the entire body — Moscow blue, purple and green are the well-known lines. Among the most striking and among the more demanding to keep well.

Guppy with solid black rear body and contrasting coloured tail — Half-black (HB)

Half-black (HB). The rear body solidly black, with the tail a contrasting colour.

Guppy with pale front body and red-orange koi-style tail — Koi / red tail

Koi / red tail. White or pale body with a red-orange rear and tail, resembling koi carp markings. Very popular currently.

Albino guppy with red eyes and no dark pigment — Albino

Albino. Red or pink eyes and no dark pigment. Albino strains are noticeably more light-sensitive and generally less robust — they benefit from subdued lighting and floating plant cover.

Panda, dragon, glass belly, blonde and many others are recognised lines or regional names, with definitions that vary between breeders and countries.

Buying: what to look for

Shop tanks of mixed "assorted fancy male guppies" are exactly what they say — fish of mixed and unknown parentage, sold on appearance. Perfectly fine if you want a colourful all-male tank. Not useful if you want to breed anything predictable.

Whatever you are buying, look at:

Fins held open. Clamped fins in the shop tank means stressed or unwell fish, and it is the single most reliable thing to check.
Full, straight bodies. Any spinal curve is a hard no — usually a soft-water grow-out problem, and it does not improve.
No red threads at the vent. See Camallanus.
Active swimming, not hanging near the surface or the heater.
What the shop's water is like. A fish moving from very different hardness to yours needs slow acclimation — ask, and check yours against the target range.

Locally bred fish from a club or a hobbyist are almost always hardier than imported stock, and often better-looking, since they were selected by someone who kept them rather than by a farm optimising for shipping volume.

Strains do not stay put

Fancy strains are maintained by selection, not by genetics alone. If you keep a mixed group and let them breed freely, the distinct patterns blur within a few generations and the population drifts back toward a greyish wild-type fish with a modest tail.

This is not a failure — it is what happens when selection stops. But it does mean "I'll buy a nice mixed group and breed my own" produces a tank of increasingly ordinary-looking fish rather than a self-sustaining supply of fancy ones. To hold a strain you keep one line, select every generation, and remove the fish that miss the standard.

The detail is in breeding and raising fry, and telling the sexes apart before they breed is covered in male vs female guppies.

One thing worth weighing before you buy on looks alone: the heavily finned strains are the fragile ones. A large ornamental tail costs energy to carry and offers more surface for fin rot, and the closer a guppy sits to the wild type the longer it tends to live. See guppy lifespan.