Silvertip tetra trauma

[Squiiggles]

So I recently bought 3 blue Silvertip tetras from one of my local shops. I am not familiar with them but I have owned lots of rasboras so I figured I would give them a try. After getting them I noticed a large lump under their abdominal area.

I don't think it's anything in my tank. I noticed it as soon as I put them up and quickly removed them.

Now I'm not sure how to sex these guys and Ivery heard they're egg laying so I don't think it's pregnant but feel free to prove me wrong!

This is a picture of one of them.. any idea?

http://m.imgur.com/wCF0gqL

 

[Autumnsky]

It looks very probably pregnant. Not an expert but I remember my Harlequin Tetra looked similar. I thought it would pop it was so huge, only to be told it was pregnant/getting ready to lay eggs.

Though perhaps someone with breeding experience might know and can share some info.