To me, this looks like a common birth defect, that didn't become obvious until it grew up a bit.
The entire body actually looks malformed.
The entire body actually looks malformed.
Thank you so much for your information and updates because this has helped me. A few days ago my healthy electric blue acara was swimming fine and then when I went to feed them in the evening I noticed he was on the floor hiding and when he came up to get food he wasn't moving his back tail and that has been the same for the last 3 days he will not move his tail at all swimming head up so I am thinking after doing some research that is the same as your fish it must have been a spine injury. I will post some pictures tomorrow in the day
