He was not eating since a few days and acting very shy. Yesterday he was resting at a more than 90 degree angle (more than vertical, belly slightly facing the surface but not completely upside-down), and before that he was often at 90 degree those last few days....but even with those strange resting positions, he was coordinated and level when he moved around (even if a little bit slow)...
Not sure exactly what happened, he was not emaciated, no bite marks, fins looking good, no rapid breathing....but the skull shape and mouth area looked a bit strange, like too much male (mouth is facing more upward on the male than the female, and it was more and more so those last days, at least I had this impression). Also, he had strange eating difficulties since about a month, like he had to "prepare" before eating with various mouth motion, and was not biting through his squid pieces as easily as before....Didn't look like overgrown teeth though, at least from pictures I got from the net....
The female red eye, guppies and amano shrimps look fine, no difference in appearance or behavior....
I suspect old age or some kind of tumor, but who knows
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