Guppy Inbreeding

There are many fanciful varieties of guppies, with “proprietary” strains being offered at almost every online site. Guppies are prolific and colorful fish, but beware when you search out these rare and unique strains. Like overbred goldfish, guppy inbreeding is rampant among these extra special varietals, so owners please be forewarned.

Why is guppy inbreeding bad?

Inbreeding, no matter what species, occurs when genetically similar animals are cross bred multiple times in order to get certain external characteristics. It could be a color or fin length in fish, and since guppies replicate so quickly, as is the case for many live bearer fish, it is very easy for even novice breeders to start to see unusual strains. However, in trying to get a particular external appearance, other inbreeding problems start to occur.

What problems does inbreeding create?

As with most forms of inbreeding, selection for particular traits comes down to DNA and genes. Dominant traits will appear most frequently, with recessive genes only making an occasional appearance. These recessive genes are responsible for the unique or rare characteristics that are seen in certain guppy lineages. However, there are more congenital problems carried by recessive genes, including growth and immune function. This leads to an increase incidence in early death for this custom breeds.


Problems with inbreeding is seen in certain dog breeds or fancy goldfish varieties. We often see fancy goldfish, such as ranchus and orandas, with their little hunched, stocky bodies, unable to have normal buoyancy function due to their breeding. They may be pretty and cute, but selecting for external appearance as significantly hampered their swim bladder function.

How can I protect my fish from inbreeding?


Well, “variety is the spice of life,” so if your population has been breeding in isolation for a few generations, it’s time to mix things up! After an effective quarantine period, introduce some new genetics into your population or swap some fish with a fellow hobbyist.

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