Black skirt tetra by itself?

[Minabug]

I've been taking care of a 55 gallon aquarium at my workplace and one of the black skirt tetras came down with what seemed to be dropsy. Treated him at home in a 5 gallon aquarium with marcyn-two and his scales and completely back to normal (no more pine coning), no more eyes bulging (and they were), and he's not bloated anymore like he was. I didn't want to put him back in the 55 gallon aquarium incase the dropsy came back, much easier manage at home. I tried to get 2 more black skirt tetras for the one in the 5 gallon aquarium since he's a school fish and he attacked them. I removed one, even with just one other in there, he attacked it. So my question is, even though black skirt tetras are schooling fish will he be okay by himself? He seems completely content by himself to me. Swims around the tank, through the plastic plant, etc. He seems more content by himself to me than he even did with other black skirt tetras.

 

[Minabug]

I should mention that this was a black skirt tetra that was donated to the tank at my workplace by someone who had 3 black skirt tetras and the 2 others died so they kept this one in a bowl of cold water for 3 months without a heater or filter, so he was by himself for 3 months before he came to the 55 gallon at my workplace.

 

[aquabeast]

id leave him that way, he probably never got time to adapt to others.

 

[Minabug]

I'm glad to know that he'll be fine this way. I just didn't know if being alone could potentially cause more harm since he's meant to be a schooling fish, even though he seems happy.