Oops, just got told it was high amonia, not nitrate. All the other readings are normal. However, he has been in his hospital tank for two weeks with no change, rather he is getting worse.
Just used Epsom salts at the reccomended amounts for three weeks.
Prior to getting sick he lost interest in food a little - still eating, but not as much as usual. He would be swimming along normally and then just take off around the tank at a million miles per hour. it was really odd.
Feeding him capsules and also frozen food capsules for oscars bought from the aquarium.
Tank maintenance - water change not as often as should (feel soooo bad now) every 3-4 weeks.
Thank you for the questions - I'm beside myself!