Just won a small koi fish and need care tips!?

So I was at the fair with my friends. We saw a cool game that gave small koi fish out for prizes and we actually won. I didnt want to give him back because the guy wouldnt take him and he said that he needed to get rid of the fish or they would be eaten. I paid, so I got the fish. I have a 40 gallon tank with lots of different fish that are friendly, except for one black tailed shark that I am thinking of giving to my friend. So this fish is small, orange and white with flowy tails. I think he is a koi, but not a huge one and he will not get HUGE. Just a small, cute little koi. I am a very good pet owner( dogs, cat, fish, horse) so I will care for him, but are they agressive? Do they eat regualr fish flakes? I have tropical fish flakes. How long do they live? Do they like lots of plants? I have tons of plants in my tank. Are they easy keepers? Will he get lonley? If he needs anything, I can just run over to the local pet store that is big on fish. I need to know all about this fish!! Thanks!