Now I take offense to that last part. I am 15 and I may not be the most popular person on MFK... admittedly I can be a bit of a douche sometimes... but you can bet that I do whatever I can to make sure all my animals are happy and healthy, and you won't see me with monster fish crammed into a 70g any time soon. While the OP may be a completely unfit fishkeeper who should probably stick to Venus Flytraps and Guppies for now (seriously OP, do us all a favor and do that, or at least don't wonder why your fish die), chalking it up to age isn't fair for those young animal enthusiasts who properly care for our animals.
OP - RIP your Channel Cat and Pacu, and in case I miss the other threads, whatever other of your fish die within the next few months, and if you AREN'T a young kid than you have NO excuse, whatsoever.