Bloated fish

[Fisherdashery]

Hi, Im a little worried about some of my fish (ember tetras, white cloud minnows) About half of them are healthy or even on the skinny side, and the other half are chubby or bloated. They all eat well and none are being bullied out of their food so i don't think any are over eating( the skinny fish eat just as much as the bloated ones)
I thought they might have been pregnant but it's been several months, way past how long google said the pregnancy term was (which i know isn't a wonderful source but they shouldn't be months off). They appear healthy in every other respect though, and don't seem in any danger of dying. They don't drift or tilt and they don't sit at the bottom all day. They can keep up quite easily with the healthier looking fish. I don't see any poop etc. hanging from any of them either. Is it just genetics or is there a problem I'm not seeing?

I'll try to get a picture but they're all so little my camera doesnt do a very good job. The two in the back there's one with a silver belly and the other is slimmer. Again the picture is really bad so if it doesn't help no worries.
Thank you guys!!

 

[Andy Sager]

The good/ bad news is these fish reproduce by laying eggs not live young so they will never be pregnant. That said, Females will be well more rounded than their male counterparts and can hold their eggs without laying them ( a.k.a. spawning) their entire lives so no worries if they don't. If you want to encourage breeding, you want to add a lot of very frilly small leaf plants which a female and male will swim in between them and spawn. Unfortunately, if you do not remove the breeders, they can eat the eggs they just spawned. Most people who have fry from these species of fish in a community tank get them by luck not skill as fish eggs are desired by and a great food source for all fish species.

Hope this helps.