There is a good reason that Alex has such good reviews. He deserves them!
There isn't much I can add to what has already been said about Alex but I will say I really liked the neighborhood he lives in. At night we went out for a walk to the plaza which is about a half block from his door. It was full of activity. It was really nice to see real Brazilians on a normal night. They were riding bikes, jogging, sitting and talking; kids were playing. Guys were playing basketball. There were lots of places to get food. And none were McDonalds. They were all locally owned, mom and pop kind of places.
Alex also provides his guests with a list of suggestions about things to see and do in Rio. I told him he could easily be a tour guide.
I also suggest you ask him about Paqueta Island. It is an island just about 50 minutes boat ride from the center of Rio. And it only costs about 6 rs.
He has a funny story to tell about the first time he hosted someone on Couchsurfing, before he began using Airbnb. He invited someone from Mexico to stay with him and his mother. He can tell you the rest of the story : )