Water parameters look good.
Arianna777 said:
His aqurium is only 20 gallons I adopted him and his old aqurium was 20 gallons too but when he goes better I already decided to buy him 40 gallons now he is in STREESS I can put him in a new aqurium
So he's still in his original 20gal or you recently put him in a 40gal then back to the 20gal?
Tank been running 2,5 month it's only him no other fishes the filtration I have for 50 gallon aqurium
Every week 25%
But last week when we treated his aqurium with Metronidozole we changed 25% every day for 5 days
What food do you feed and when is the last time he ate? Depending on this answer I would do one of the below options. Bear in mind this is only my opinion and what I would personally do in the situation.
1. If he has eaten recently: put salt (sodium chloride) in the water @ 1 Tablespoon per 5gal of tank water, keep feeding as normal. Look for improvement in the next 5-10 days.
2. If he hasn't eaten in weeks: in this case the fish would be doubly weakened since he's also been treated with meds that didn't help. IMO the outlook for survival isn't as good as if he is currently eating. But I suppose I would try API General Cure and hope that by some miracle he improves.
I wouldn't do both salt + meds together. I hope your fish survives.