Is my Molly Prego?

[martiniduck]

I posted yesterday about my new tank and what to stock. Today I noticed that my Molly was acting strange and looking different. He/She belly has grown considerably, since I purchased it a week ago. It is been resting on the gravel except at feeding time. Then it gorges itself. Swimming as fast as possible after every last flake. The only other fish in the tank with it is a male swordtail. My questions are... 1. How do you sex a Black Molly? 2. Can a Swordtail mate with it? 3. Is my fish prego., sick, or just fat?

Specs: These are the first two fish after cycling the tank. I have recently did a 20% water change. I have hard water and my water goes through a water softener. Today's readings are PH 8.2, ammonia 0, nitrite .25, nitrate 10. 29 gallon tank.

 

[ElwoodPDowd]

It could well be pregnant, but I tend to find mollies don't spawn until they're settled in to the tank's chemistry, which can take a while.

Sexing mollies and other livebearers is easy, look for the anal fin. If it's fan-shaped and coming away from the body, it's a girl. If it's thin. straight, and held flat to the body it's a boy.

Swords and mollies are different species, I've never heard of them breeding successfully, but that's not going to stop them having a good old college try anyway.

Mollies can breed in a special way; the males can deposit a sort of slow-release package of sperm so the female can get pregnant 3 or 4 times with no male present. Often, mollies bought from shops are pregnant already.

Keep an eye on her size - if you've a phone camera or digicamera, take photos every couple of days and you'll be able to tell if she's growing (pregnant) or just likes to eat.

Oh, and depending on what you're planning to stock, you might want to consider converting your tank to a brackish one (has some aquarium salts in, but not as much as marine systems). The molly and sword will greatly prefer it and will live longer, happier lives. They will live in freshwater, too, and chances are your fish shop were keeping them in freshwater. But to see the best of most livebearers, slightly brackish, hot, and dim conditions wll make them feel right at home (invest in a few floating plants, they'll love the shade, dappling, and food offered by the roots and if they do spawn, the fry have the roots to hide in).

 

[martiniduck]

I tried to take a picture, but my auto focus will focus on the glass and not on the fish. Do pregnant mollies like to rest a lot on the ground? The only time she moves from her little hidden area is when I feed her. Then she comes out and eats like a pig, zooming around the top of the tank feeding. Other than the non-activity she looks fine.

 

[colematthewmalaka]

There's a chance she's pregnant. I would put her in a separator so that she doesn't give birth and have her babies eaten. If she is congrats.