I'm interested to see where this goes . . . I had a blue acara who very gradually stopped swimming, and eventually rested on the bottom of the tank full-time, but not on his side; he was sitting upright, just not swimming.
I eventually moved him to a smaller tank where I could keep an eye on him. he would spend most of the day sitting in a flower pot, and when I dropped in food - - sinking pellets, of course - - he would come out of the cave, eat and go back in the cave; never leaving the floor of the tank
eventually, he lost the ability to sit upright, though he kept eating . . . he recently died, but now I'm wondering if there was something else I could/should have done . . . ?