My Oscar is acting very funny

Question
I have a breeding pair of Oscars for about two years Sushi 10" and Champ 9" along with a small pair of green spotted puffers.In a 100 gallon tank. I had just recently discovered my Oscars were a breeding pair about 2 months ago.  My Oscar sushi which has been showing me very bad signs lately as if she can't breath and she shakes her tail rapidly like she were constipated. I was at work the other day and my roommates said that my Oscar had swallowed one of my puffers and chomped its back tail off. RIP coheed my puffer he had died that day before i got home. I just didn't understand my Oscars had gotten along with them for 2 yrs. I just wanted to know what I could do to help Sushi.Champ has been doing fine acting like he always does swimming crazy.

I've been researching and found that puffers are poisonous to other fish. I hope that there might be some other problem then my Oscar being sick from my puffer.

Answer
Brian,                                                                 Unfortunately no matter how well they get along if she gets hungry and it fits in her mouth she will try to eat it so will champ.Yes puffers have toxins in them.They are very poisonous. Since puffers skin is very thick hopefully it will pass with as little poison as possible going through her. She probably didn't chomp through puffs skin since she doesn't have teeth like a piranha. I think it is just going to be a waiting game now....hopefully she will come through it ok. Good Luck,Tina