Is She Pregnant or Just Fat? The Definite Guide to Guppy Bellies

If you have female guppies in a tank with a male, the answer is almost always “Yes, she is pregnant.”

But beginners often panic. You see a female getting huge, and you wonder: Is she about to give birth? Is she just overfed? Or worse—does she have Dropsy?

As someone who watches thousands of guppies in the shop, I can tell you that pregnancy has a specific “look.” It’s not just a big belly. It’s a shape.

Here is how to tell the difference with 100% accuracy.

Sign #1: The Gravid Spot (The Truth Teller)

The “Gravid Spot” is a dark patch near the anal fin (the bottom rear of the fish).

• In Early Pregnancy: It will be small and might look light grey or orange.
• In Late Pregnancy: It becomes dark black or deep maroon.
• The “Eye” Test: If you look very closely (or use your phone camera to zoom in), you can sometimes see tiny black dots inside the gravid spot. Those are the eyes of the fry looking back at you.

Note for Gold/Albino Guppies: If you have Albino or heavy gold strains, the gravid spot won’t be black. It will be a bright red or orange color.

Sign #2: The “Boxy” Shape (The Square Stomach)

This is the secret most people miss.

• A Fat/Bloated Guppy looks like a balloon. The swelling is round and smooth, like she swallowed a marble.
• A Pregnant Guppy looks like a Brick.

As the fry grow, they push against the mother’s ribs. When she is 2–3 days away from giving birth, her belly will look almost square or “boxy” at the front. If you see corners on her stomach, get the breeding box ready.

Sign #3: The “Anti-Social” Behavior

Watch her personality.

When a female is close to dropping fry (labor), she changes:

1. She stops eating (or spits food out).
2. She hides near the heater, behind the filter, or in the floating plants.
3. She stays still in one spot while breathing heavily.
4. She gets aggressive if other fish come too close.

If she is huge but still actively chasing food and swimming with the pack, she is likely not ready yet.

The Danger Zone: When It’s NOT Pregnancy

Sometimes, a big belly is a death sentence. You need to rule out these two killers immediately:

1. Dropsy (Pineconing)

Look at the fish from directly above (top-down view).

• Does she look like a smooth torpedo? (Good)
• Do her scales stick out like a pinecone? (Bad)

If the scales are sticking out, her organs are failing and retaining fluid. This is Dropsy, and it is almost always fatal. It is not pregnancy.

2. Bloat / Constipation

If the belly is huge but there is no gravid spot (or the spot is very small), check for poop.

• If she is trailing a long, stringy white poop, she might have an internal parasite or severe constipation.
• Fast her (no food) for 24 hours and feed a tiny bit of boiled pea (skin removed) to clear the blockage.

The Timeline: How Long Do I Wait?

In Malaysia’s warm climate (27°C – 29°C), guppy pregnancy is fast.

• Cycle: 21 to 28 days.
• Cooler Water (Air-con room): Can take up to 35 days.

Shop Guy Tip: Do not move her to a breeding box or small container until you see the “Square Belly.”

If you move her too early (when she is just round), the stress can cause her to abort the babies or absorb them. Wait until she looks like she is about to explode.

Summary Checklist