Is guppy pregnant or is it something else

[Melissan76]

I purchased my female guppies about 3 weeks ago and this one her belly is huge. I can't tell if she is pregnant or not. She swims around a little but mostly stay at the bottom and seems to be breathing faster than the others. I have them in a 5 gallon tank the ph is 8.2, ammonia 0, nitrites 0, nitrates 5.0. There are 4 female guppies and 1 nerite snail. Any help is appreciated.

[Radagast]

she looks big but from what i'm seeing the Black spot isn't being shown.If she is pregnant the black spot is the best way to tell.sometimes the spot could be pink if her coloring has made it so. Really she could just be a bigger fish.Do any of the others have a black spot on their underside by their vents? Was these females in a separate tank from the males at the store you got them from?

[Fishbait]

Yeah she looks like mine that gave birth but yeah mine had the black spot. She gave birth twice and I have 8 that survived and she died giving birth. They are super hard to see the babies too. They would stay at the top of the water behind my filter. Really tiny at first.