How Long Are Molly Fish Pregnant For—How Can You Tell

How Long Are Molly Fish Pregnant For—How Can You Tell

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Aquarium fish vary in the way they reproduce.

A majority of the species lay eggs, which hatch into young ones, with the eggs either blown into a bubble nest like in betta fish, bred in the mother’s mouth by mouthbrooders like cichlids, or even in caves or on aquarium plants.

Then there is the class where mollies fall of livebearers, which give birth to live fry. Usually, you’ll here fish keepers say their fish is pregnant, though the more appropriate word is gravid.

That said, it can be quite challenging to tell if your fish is gravid, particularly if you do not have an experience keeping livebearers. Mollies are especially ‘cream-of-the-fish-hard’ to tell when pregnant, more so, during the first few days.

Overall, a typical molly fish pregnancy will last between twenty (20) and forty days (40) varying between different fishes and species. Read more about molly types here.

With every pregnancy cycle, a healthy molly female will birth anywhere from twenty (20) to 100 babies, and can continue breeding for between 2 (two) and 2.5 years; their average lifespan is 3 years.

So, how do you know if your molly fish is pregnant (gravid) you ask?

Below are a few classic signs you molly will show. (will look at them in more details a while later)

  • A gravid molly will have a change in behavior, usually becoming slower, and tend to hide more than is normal only coming out to feed.
  • Your fish might also become more aggressive to tank mates, particularly those that venture into her hiding spot.
  • You’ll notice a dark triangular spot appear near a pregnant female’s anal vent called the gravid spot. But please note that the point might be quite challenging to identify on individuals with darker colors like black mollies. In which case, you may just have to rely on other signals to be sure.
  • As you would expect, the gravid spot will get bigger and darker as your fish nears its birth date. So if it is clearly visible, then your fish is almost ready to release its babies.
  • A pregnant molly will also take a rounder, more full-bodied shape, and the stomach will especially grow bigger and seem stretched out.
  • On lighter colored mollies you might even be able to see the eyes of fry through the belly as it stretches.
  • They will also develop a black line on their bellies, again, this will not be visible in black mollies.

How Long Does It Take Molly Give Birth

As I’ve mentioned above, mollies are usually pregnant for a period anywhere from 20 to 40 days (average 30 days). Of course, that would be how long they’ll last from conception to birth.

But before this period, there is usually a courtship period between the male and female molly, which can last another couple of days.

Usuallly, the courtship period is characterized by a couple of chases every now and then, which is quite often accompanied by milds displays of aggression.

This dance only ends with the beginning of breeding, and then followed by the said 30 days (on average) where the female carries the eggs in her stomach up to when she gives birth to live young ones straight into the water.

How To Tell If Your Molly Fish About to Give Birth

Through out the gestation period, your molly fish will show several changes in behavior (as discussed in the intro), though some will be only apparent closer to the ‘day of birth’ than others.

The change in behavior will start from the moment your fish breeds, sometimes from courtship, then escalate as it gets closer to releasing the babies.

However, the clear sign that your molly is ready to give birth is when the gravid spot is visibly dark and large, and the fry eyes are visible through the translucent belly edged close to the gravid-mark.

Around the same time, but a little earlier, your molly will also be quite rounded with the belly visibly large from the eggs she is carrying inside her.

A few days before your fish give birth, you may also notice her bulge (V-shaped) below the gills and her outline becoming fairly square around this region. This happens together with the gravid spot changing in size.

How Mollies Act Before Giving Birth

It is difficult to tell whether a molly fish is pregnant, but as we’ve seen, there are several clues you can look out for. Some are physical, while others are behavioral.

And since we’ve pretty much discussed the physical signs above, let’s take a quick dive into the behavioral clue.

For starters, almost all tropical fish kept in aquariums get aggressive while breeding and mollies are no exception.

However, you will notice that mollies hide more as opposed to getting into a confrontation with tankmates. Usually, the hiding is more apparent closer to a fish giving birth.

Therefore, ensure there is a generous amount of plants and decorations in your tank for the fish to get a hiding spot when its time.

From my experience, mollies also seem to prefer hiding in dark spots in the tank as opposed to well-lit areas. I bet they feel more secure and comfortable in that setting.

That said, it is advisable to separate the pregnant fish from other adults for specialized care and to also ensure she does not get stressed out by the rest.

It will also help you feed your molly more comfortably without the stress of other fish, which are able to swim faster than her.

Molly Fish Babies

Since mollies are livebearers, same as guppies (see how to breed them), least killifish, and platys, they do not lay eggs but instead, release live babies in the water.

Sadly, the babies do not get parental care from their mother and are as likely to be eaten by the parent as they are by other fish in the aquariums.

Therefore, you will need to give them parental care if they have even the slightest chance of survival.

A breeder box will help you keep the molly babies fish once the mother has released them. Placing the mother in a breeding tank away from the rest of your community also goes a long way.

You can also use a net to remove the mother from the breeding tank once she has dropped the babies, though I find a breeding box more effective and less tasking to use.

Once the fry are released, they automatically fall into a different compartment away from the mother, where you can keep them until you catch and move the adult fish into the main the tank.

Once the babies are large enough and can fend for themselves, you can move them back to the main aquarium, but make sure there are enough plants for the fry to hide in.

A few other things that are crucial to master when caring for molly babies are tank maintenance and feeding.

Make sure your water quality remains safe by performing regular water changes. Start them soft food in tiny pieces that the fry can consume.

Do Moliies Eat Their Babies

Apart from not giving their youngs parental care once they are born, mollies are cannibalistic, and a mother will eat her fry if given a chance.

As such, using a breeder box is highly recommended, and move the adult once she has dropped all her babies.

Thats all, have fun keeping mollies.

Eddie Waithaka

Resident Content Creator and Marketer at AquariaWise who talks about aquariums and fish and aquascapes a lot.

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