I have a 18 inch Red Bellied Pacu Named Reggie. The guy who used to service my tank has disappeared and left me on my own to take care of it. This would be fine, but now Reggie is belly-up in the tank with slow breathing, a clouded up eye that he cannot see out of and his fins are fraying away. I've gotten help from others on an online fish site (thegab.org) but they say it's best to talk to someone who knows large fish. I've done a 50% water change today and that's all I've done. I bought some Maracyn and aquarium salt but haven't used them yet. The people said to wait and the water change might be all he needs. But he looks pretty bad so I would really like to know if I should treat with the meds and salt. His tank temp is around 77 and the water test showed everything was normal except the ph was at 6.0 and the ammonia was between .25 and .50. I don't know if this was the problem but I really need help to save this fish, he's huge and really beautiful. I've had him for 8 years. Usually he's pretty hearty and any weird stuff I see on him is gone the next day, but this time it looks like he can't fight whatever is killing him. Mostly I wanted to know, what can I do for him now that will help him or have I done everything I can? He looks pretty bad. Thanks for any advice.