Hello again. Well, stick focusing on Nemo, my 11" Oscar who has been jerking his tail, has trouble seeing and grabbing his food (won't eat his pellets when they are hard, he waits till they get soft and then tries to grab them and sometimes he does manage to eat one or two. I finally decided to try crickets again. He got so excited to see me with bag as he always did. When it came to grabbing the crickets, he kept missing then got really mad and grabbed one. I got happy until the cricket just walked right out of his mouth after about 1 minute. Has he lost strength? He managed to keep down the crickets that the other O crushed and broke in half but when it comes to the live crickets, he seems not to be able to crush them in his mouth. My final conclusion after following everyone's advice is that he probably got a disease from a feeder fish that probably damaged his nerves somehow cuz his tail keeps jerking really hard out of his control (like someone with parkinsons. He is not breathing heavy but his tail jerking keeps pulling him down. You can see video link below:

having been exposed to high ammonia, it is possible that he had some
internal injury.... the good news is its trying to get some foods and a
big chance to survive... i get back to the video and it seems doesn't
seeing the thing in front of it....

yes, he is still crashing into things. i just saw that the dead cricket that he took in his mouth is still in his mouth. don't know if he is not able to swallow it. should i try giving something easier to swallow?