Selecting the Best Parental Resources for Breeding Double-Tailed Betta Fish

icon author linh nguyen

By Linh Nguyen Updated on 09 Feb 2023

Breeding double-tail bettas can be a fascinating and rewarding experience, whether you're an experienced aquarist or looking to start your own line of super-colorful Siamese fighting fish. Double-tail bettas are attractive and desirable in the marketplace because they break away from traditional single-tail varieties with their two separate caudal fins that flare out like wings – creating an eye-catching display.

But what's involved in breeding these intricate and vibrant creatures? It turns out there’s more than meets the eye when it comes to the origin story of this captivating fish – they were actually bred through carefully thought-out genetics! 

Read on for more information about the anatomy of the double-tail betta along with tips for proper care and successful breeding strategies! Let's dive into the world of gene selection and learn about what makes double-tail betta fish so special!

A beautiful double tail betta fish

A beautiful double tail betta fish

1. Selection of brood fish

The doubletail is made when a gene changes and makes the fish's tail have two parts. Another change that this makes is that the fish has a much bigger dorsal fin. When the top half of the betta mutated, it also changed the bottom half to have another tail and anal fin.

According to this theory, the dorsal fin of a double-tailed fish is several times wider than that of a single-tailed Betta. In fact, the dorsal and anal fins in the double tail appear to be roughly the same size and width.

The mutation that produces the double tail is recessive compared to the common singletail. Dual-tail x single tail will produce 100% single tail, about 75% of which will carry the recessive double-tail gene.

I used to think that breeding a double-tailed male with single-tailed females would produce 100% double-tailed genotypes, but I tested it by breeding the same male (single-tailed/double-tailed) with two female siblings from the same colony. One hen produced 25% of the double-tails from the litter with this male, and the other hen produced no offspring, indicating that the double-tail gene did not transfer.

I then took a double-tailed male from the first pack and bred it with a single-tailed cousin, to reassert, and got a large swarm without any two-tailed individuals. Therefore, as was assumed earlier, I can only conclude that the double-tailed gene does not affect all members of the flock.

The first generation of the ST/DT cross is considered to be a single-tailed doubletail, or ST/DT. Breeding two ST/DTs will almost always produce some DT fry (about 25%). Breeding a DT (or DT/DT) with an ST/DT usually produces a high amount of DTs, up to 50%.

Breeding within the same species usually gives you 100% of that species, but crosses like this very often have genetic problems, such as fused lobes, scoliosis, or body deformities. These problems can be limited in intraspecies populations by crossing only unrelated fish that do not carry serious defects.

The common practice today among ornamental betta breeders is to use Double-Tailed (DT) to improve their Single-Tailed (ST) lines by increasing fin size and dorsal fin width. This can be accomplished in the F1 generation, but selective breeding can be extended so that the ST Betta has a dorsal fin nearly as wide as the DT!

A promising new development is the Halfmoon (HM) x Double-Tails ( DT), with its plump, stacked caudal lobes that can spread up to 180 degrees or more. This combined with the symmetrical proportions of the dorsal and anal fins makes for an impressive betta!

2. Undesirable defects

Although it is sometimes difficult to determine which fish will do best when the flock is young, extreme predictability is eliminated when working with double-tails. Major faults can be detected as early as a few weeks of age, and those individuals must be removed from the flock so that the breeder can focus on better ones.

The most common defects in double-tail fish are an irregular caudal lobe,  Y split, crooked spine, a deformed body, and a fused caudal lobe.

2.1. Irregular caudal lobe

This is one of the most common problems in Doubletail fish. In this case, one caudal lobe is significantly smaller than the other, in most cases, the lower lobe is larger.

The degree of difference between the two lobes varies, sometimes it is almost imperceptible, and in other cases, the upper lobe is so small that it looks like a tiny "thumb" stuck to the tip of the lower tail. While a small difference in size between these two lobes is acceptable for show purposes, a large difference is considered a serious fault.

Irregular caudal lobe

Irregular caudal lobe

2.2. Y- split

These caudal lobes, even though they are even, are small and spread out at awkward angles, which prevents them from achieving a stacking effect. Breeds like this often do not have enough fullness and branching to create quality offspring, so it is best to remove them from your breeding program.

Y- split

Y- split

2.3. Scoliosis

This error can usually be detected by looking at the fish from above; the tip of the spine near the tail is sometimes slightly "kinked". It also looks like a small bump on one side of the fish.

This particular problem is so common in DT that a slight curvature would not be marked by the referees. However, abnormalities are also occasionally present in ST bettas carrying the DT gene, and this would be a fatal error. A DT with a very crooked spine should not be used for cross-breeding, as it will pass on this trait to any progeny.



2.4. Disability

Another common problem with using double tails in breeding lines is the severe spinal deformities the fish can have, where their spine will curve and sometimes appear twisted.

Besides, the body is also much shorter and thicker. In fact, the deformed double-tail is often compared to the dwarves of another species.

These fish should never be bred, as a faulty transfer can completely destroy your aquarium line. However, most of them seem to be happy and healthy despite their deformities and can make wonderful pets.



2.5. Fused caudal lobe

This is what happens when the DT trait is incompletely expressed: the caudal lobes are fused rather than evenly separated, the degree of which varies.

A betta with a fully adherent caudal lobe can be difficult to distinguish from an ST, you must look for other signs, such as an extremely large dorsal fin or a short body.

Those whose caudal lobes are approximately half-fused are sometimes referred to as "Heart-tails," but this is not considered a betta trait and should not be sought after for show purposes.

Fused caudal lobe

Fused caudal lobe


From the initial selection of parent fish to the process of incubation and eventual fry distribution, the breeder has much work to be done. It helps to plan ahead and stay organized when breeding double tail bettas, as this will give you the best odds for success.

With consideration of the different methods discussed above, you can easily find the right path to success for your double tails. That said, adding the right equipment like aquarium tanks and filtration systems is also a great way to ensure your fish’s long-term health and happiness.

Finally, with enough determination and some luck, breeders can produce healthy and unique double tails that stand out in any aquarium!

If you need more help or advice on this topic, feel free to let me know in the comments below. My goal here is to continue to provide further resources so that all betta lovers have access to the best options for their fish’s well-being. No matter what route you take, I wish you all the best of luck!

Leave a comment

Your email address will not be published. Required fields are marked (*)

Please fill out this field.
Please fill out this field.
Please fill out this field.