[kobeBean]

I recently purchased 8 cardinal tetras. I've noticed that a few of them have this brown darkish belly that bulges out below their bottom red stripe. Is this normal? Sorry for the picture quality, having a hard time getting them to stay still..

 

[Diana]

No, that is not normal.
Not sure what is wrong, though.
Have you seen the poop?

What are your water parameters?

 

[kobeBean]

I actually haven't seen the poop yet.

Water is good but a little hard.

Nitrite: 0
Ammonia: 0
Nitrate: 10 ppm
pH: 7
KH: 80
GH: 160

I notice that about half of them have these dark bellies. Could it be that they're constipated?

 

[lksdrinker]

That does look odd. Maybe try feeding some cooked/peeled peas in case it is constipation. I remember seeing another thread at some point this week where someone referenced brown neons and/or cardinals. Cant recall what the issue was there though.