Make or Female Guppy?

Hi, apologies for what is very likely a silly question, I’m quite new to owning fish, I currently have a tank with 1 Loricariidae catfish, 3 neon tetras and 5 guppies. One of my guppies has grown quite a lot, and appears to be pregnant, I have done a little bit of research and the symptoms check out, it seems to be sitting on the tank floor quite often, flutters about a bit, rubbing against objects and the side of the tank, and seems to be followed by another guppy. I’ve looked for signs that it is a female, as we bought them imaging they were all males, but physically it seems to be male?

I imagined it was possibly just bloating, but it seems to have continuously grown larger. If someone could help me identify what’s going on that would be really useful , pictures attached.

Guppies are probably the easiest fish to sex, although ironically, its a bit difficult to tell from your photos!

This might help.



Males have a gonopodium which extends and impregnates the female.

Lunar Jetman said:

Guppies are probably the easiest fish to sex, although ironically, its a bit difficult to tell from your photos!

This might help.

Males have a gonopodium which extends and impregnates the female.

Click to expand...

From that diagram I can pretty surely conclude that it’s a male, in such instance, what would be the diagnosis for this issue? See original post for symptoms.

Thanks for your reply, much appreciated. Apologies for the terrible photo quality, fish won’t stay still. Especially this one

It is hard to see from the photos but do his scales stick out so that when you look at him from above he looks like a pine cone?

Another possibility is intestinal worms. When he keeps still (or any of the other fish) can you see tiny red things protruding from the anus?

LOL on the girl bits and boy bits

The guppies in the pictures are males. Males have big colourful tails and more colour on the body.
Females have much smaller more rounded tails and very little colour on the body.

And the anal (bottom) fin is long and slender in the males and is called a gonopodium.
The female's anal fin is fan or triangular shaped.

essjay said:

It is hard to see from the photos but do his scales stick out so that when you look at him from above he looks like a pine cone?

Another possibility is intestinal worms. When he keeps still (or any of the other fish) can you see tiny red things protruding from the anus?

Click to expand...

Cannot see any red protrusions, nothing noticeable, I have separated him from the rest of the tank, will leave it there overnight and check on him tomorrow. Another fish in the tank also has a bump on the underside, only much smaller and it doesn’t seem to be an issue. I will cut down on feeding him if he survives past tonight, potentially it could just be that he is overfed, we shall see. Any other suggestions would still be fantastic, as I have no clue.

Lames said:

View attachment 94102 View attachment 94103

Cannot see any red protrusions, nothing noticeable, I have separated him from the rest of the tank, will leave it there overnight and check on him tomorrow. Another fish in the tank also has a bump on the underside, only much smaller and it doesn’t seem to be an issue. I will cut down on feeding him if he survives past tonight, potentially it could just be that he is overfed, we shall see. Any other suggestions would still be fantastic, as I have no clue.

Click to expand...

That sounds good. When I have a fish that I accidentally overfed, I fast (or don’t feed) them for about 3 days. This will make the bloating go down, and give him time to recover.

I agree with Essjay with intestinal worms being likely. I would get a de-worming medication and treat all the fish (if one has it, they all will have it). Let us know how he gets on.

He’s survived the night, not much noticeable change, though I think the bulge has lessened somewhat, so I’m leaning towards this just being a bad case of overfeeding, I shall leave him in containment for another day or so and monitor him.