HELP! 7 year old O looks like he's on his way out

[JZ1276]

I've had my albino oscar now for 6-7 years. He's in a 75 gl tank with a blood parrot and bichir eel. Water levels and temp are good and I do changes regularly. The other 2 fish are fine, but the oscar hasn't eaten in over a week. His mouth is always open like he is gasping for air and he pretty much just stays in the same spot in the bottom of the tank and doesn't swim around anymore. I had been feeding him frozen cubes for a long time, tried switching it up but he still will not eat.
If it helps any, heres a short clip of him and what looks like him gasping for air.

[TheNight]

Oh wow, he has some disease. Hole in the head? I suggest doing a large water change.

[Crispy]

very large and frequent water changes is your best solution at this point. looks like he's got pop-eye pretty bad among other things. it may be too late, but best of luck.

[Lady Hobbs]

He's definately struggling but guessing to what could be wrong is not useful at this point. But I agree to a big water change to see if it can help. Do you know where your nitrate level is at?

[JZ1276]

Nitrates were low (around 10) before I did a 3/4 water change the other day. I'll do another one tonight. Could he just be old which is why he's dying?

[Lady Hobbs]

Some times fish just die and we never know what happened.
viral, bacterial, parasites, tumors, cancer......too much to ever know.

[JZ1276]

What could be causing his mouth to stay open like that??

[Lady Hobbs]

Looks like he's gulping air. I've had fish do the same thing.

[JZ1276]

After 3 major water changes since starting this thread, he looks to be recovering. I threw in some feeders hoping to get his appetite going but he hasnt touched them. He is much more active but still does not close his mouth.

[gm72]

Feeder fish are not very nutritious for the fish and will serve to increase the risk for the introduction of disease/parasites.