Sigh...I have seen this look before

[Whatigot]

Originally Posted by GreenSpottedPuffer

Anyone ever noticed a dark spot on their CCB before it died? I have seen this in a previous one and now in this little guy. Its kind of a darker area (easy to see on the white) about half way down this body. Its under the skin and almost looks like something inside him ruptured.

Oh and he is "swimming" upside down and sideways today

totally...
I had almost thought someone had stung him or something as he had been eating fine up until one day, randomly, he started to act as you have described.
Never really considered it might be cyanide...