Pregnant fish

Is there something like pregnancy in fish? If yes, How do I know I am pregnant and not fat?

Well, pregnancy in fish is natural, and we have a wide range of aquarium fish that get pregnant. They are referred to as Livebearers.

The good news is, there is a way you can identify pregnancy in fish. That is what this article is about! To make it simpler and easier for you, I will take you through steps that will help you make a sound judgment in this matter.

Here we go!

Livebearer… or not?

There are over 32000 known species of fish that reproduce in various ways. Identifying the type of reproduction strategy your fish employs will help you know which to watch out for. 

According to Wikipedia, livebearers are aquarium fish that retain eggs and give birth to live, free-swimming young fish. 

You should research the type of reproduction your specific fish goes through. Are they livebearers or not?

The most common examples of livebearers among aquarist include:

  • Mollies 
  • Guppies
  • Platies 
  • Swordtails
  • Endler’s livebearers
  • Mosquitofish

Is your fish male or female?

The next step (after determining that your fish is a livebearer) is identifying the gender. Different species have various distinguishing aspects when it comes to gender differences. The most common difference I know is vibrant colors and large bodies of males in most species. 

You should find out the particular gender difference your fish has so that you better distinguish the gender.

Identifying the gender will simplify your chances of noticing pregnancies early. In most aquarium fish, the females shoulder most responsibilities in reproduction. The female fish will either become pregnant or incubate eggs in their mouth until they hatch into young ones.

Some male fish, for example, sea horses and pipefishes, become pregnant instead of their female counterparts. 

Signs of pregnancies 

Finally, we get to the telltale signs of pregnancies in fish. These signs are evident in most types of fish. I picked some of them up through my own experience, while some result from the research I did sometime back.

Enlarged abdomen/ Mouth

Expansion of the abdomen is the most telling sign of all. If you notice your female (or in some cases male) buddies are getting fatter by the day, especially at the area close to the anal fin, chances are you will have some fries soon.

The abdominal area between the anal fins and operculum is famously known as the gravid spot/patch. During pregnancy, enlarged discoloration of the gravid spot is observed. The discoloration is present in some species of fish even before pregnancies though it still extends during gestation.

In mouthbrooders, they will refuse to eat anything you give them for weeks. It not because they did not want to; they just can’t. Their mouths will stay closed, and their mouth area enlarged significantly. The situation will remain until the eggs in their mouths are ready to hatch.

Limited social interactions

If you are keen, you will notice that pregnant fish tend to shy away from others. They will prefer to quarantine themselves in less populated places of the tank for long periods.

It is regarded as a strategic type of protection due to its vulnerability. For instance, you will find that a male will chase any other fish while the female is pregnant or incubating eggs in their mouths.


Pregnant fish will get more tired and sluggish as the pregnancy advances with time. A fish that was once hyperactive and vibrant will act in contrast to what you are accustomed to. 

Increased lethargy is a sign of impending birth. You should provide private space for your fish to give birth, whether in the form of another unoccupied tank or plastic divider. Letting the fish give birth in peace is the most you can do to help in such a situation.

Final thoughts

Most livebearers will eat their young ones after they give birth. A breeder or even average aquarist should ensure that the adults are separated from fries immediately after completing delivery.

The best way to keep the young fish safe is by keeping them in their tanks. You will be in a good position to care for and feed them if you do so. 

For aquarists with no spare tanks, You should install breeding dividers or even plastic mesh in tanks to give fries a haven. You don’t need to worry after setting this up. Young fish will naturally seek safety when in imminent danger.


For a new hobbyist, getting your first baby fish is an incredible experience. At least for me, it was. Be proud that you have sought more information. Information that will prepare you well for oncoming young ones.

I hope the above guidelines and tips will make it easier for you to determining pregnancies in your fish. These steps will come naturally with more practice. You dont have to worry about getting it right the first time.

Apply what you gain every day, and soon enough, you won’t need people like me to guide you. You will be a master of your craft…and hobby!