Betta and Pleco are fighting

Question
Hello,

I've been keeping a 35 gallon tank for a few months. I don't have very many fish (under a dozen and all of them are small).  Two of my fish are a male Betta and a small Pleco. The Betta has always seemed curious about the Pleco and would kind of nudge him from time to time. The Pleco usually just moved away and tried to ignore the Betta. Today I noticed the Betta was chasing the Pleco and the Pleco was fighting back and being very rough with the Betta.

I put the Betta back into the little cup he came in and was wondering what I could do. All of the fish have plenty of room and lots of plants to hide in. I've noticed some slight fin damage on the Betta, so I am hesitant to put him back in the tank. Is there any reason why these two fish would suddenly hate each other? Can it be helped?

Thank you for your help.

Answer
Some fish just don't get along. You can have him in the same tank but just separate the two. You can try to de-introduce them after a while. I think you might need to supply more hiding places (rocks and caves) also plants so they can get away from each other easier. The male fighting fish also like to clone territory.