Anyone know why this guppy is so massive?

[acro]

So, here's one of the oddballs in my mum's tank. We just noticed this guppy one day as it never stopped growing! The video doesn't do it justice, in person it looks even bigger compared to the rest of the guppies. It even makes the cardinal tetras look tiny!
We considered maybe she's a different species of fish that just got mistakenly caught as a fry when we purchased other fish, but the shape doesn't match platies or mollies or anything, it just looks like an especially round guppy to me.
I would assume from the shape that it's a female, although there's no gravid spot that I can see. She's just the big boss of the tank that attracts the boys and eats the fry that don't hide fast enough.
Any ideas on how or why her size came to be?

 

[Colin_T]

Looks like a male and could be just fat or have a growth inside it, or have a bad case of round/ thread worms.

To sex guppies, mollies, swordtails and platies, look at the anal (bottom) fin. Males have a long straight anal fin.
Females have a fan/ triangle shaped anal fin.

I would deworm the fish and see what happens. Section 3 of the following link has info on deworming fish.

What to do if your fish has Stringy White Poop.

Fish do a stringy white poop for several reasons. 1) Internal Bacterial Infections causes the fish to stop eating, swell up like a balloon, breath heavily at the surface or near a filter outlet, do stringy white poop, and die within 24-48 hours of showing these symptoms. This cannot normally be...

www.fishforums.net

 

[emeraldking]

It's just a late male. Late males tend to grow up large and have the build of a female for a long time but no gravid spot will be seen before the male traits will appear. Nothing to be worried about... From time to time, a late male appears from a batch of offspring. That's normal.

 

[10 Tanks]

Hello acro. This is likely a hybrid of some kind. Possibly with a Mollie at some point. Mollies are larger and if someone was interested enough in crossbreeding a Guppy with a Mollie, you could easily create a much larger Guppy. Guppies can be crossbred with several fish that are similar to them genetically. Still, it looks like a nice fish.

10 Tanks (Now 11)

 

[Magnum Man]

agree with TANKS... even if it wasn't such an extreme cross, there is a subject called "hybrid vigor" it's the same for plants, cattle, & fish... often hybrid "things" grow faster & larger, than their parent's