I have had my oscar, Redman, since he was a baby, he is now 9-10 inches. His tank mates from the start have been kuhli loaches, dojo loaches, hillstream loaches and some upside down catfish. It was an experiment I ran to see if an oscar would get along with the other fish if it grew up with them. Until a few days ago, Redman has been a buddy to everyone in the tank. He started to flare (mouth open real wide) quite a bit more than usual and began to harass the dojo loaches and only the dojos. I hoped it was an oscar mood swing and observed. Yesterday, Redman started to do quick circles (like a dog chasing its tail)(sometimes he spins left, sometimes it's to the right) for about 5 seconds while flaring and he began to take shots at the dojos. Thinking that he developed an issue with the dojos, I moved the dojos to their backup tank this morning. Redman continues to do his circles and flaring even with the dojos removed. The frequency of his spins has also gradually increased. He leaves the other fish alone, it was only the dojos he targeted.
Parameters - Nitrate - 40, Nitrite - 0, Ammonia - 0, gh - 200, kh - 100, ph - 7.0, temp - 78F
There has been no changes to the tank besides its weekly water change for well over a year now.
Has anyone run into this behavior before? I have seen him go through mood swings before, he is an oscar, but never like this. Frantic is the word that comes to mind when he starts circling.