Acting Strange And Fin Splitting

[aquanavy]

My German blue ram has been acting strange, I bought him a month ago and all of a sudden a week ago he started getting aggressive and his colors got really vivid. That went on for two days and he was biting all of the fish, I also noticed that in the process, his fins were split. After two days everything was normal, and his fins weren't split. It just so happens his fins split again and he is aggressive and really colorful. Can anyone tell me why this is happening?

 

[star4]

What other fish is he in with? Fins can get split easily with flaring and chasing other fish.

 

[aquanavy]

There are corydoras, neon tetras, rummy nose tetras, and a bristlenose. But the only fish it chases are the corydoras