Unless your tetras are some of the smaller ones like neons, they will be fine with the angels. Even black neons are fine with an adult angel. I always keep my bettas in community settings and they don't give me much trouble. Your total fish load is heavy but not to the point of being a real problem unless the thirty-leven tetras are expected to go over 1 1/2 inches as adults. With proper care as they mature,you may find that all works out fairly well for you. With any group of fish that big, you will lose a few before they are fully grown so you might want to wait and see what is left when they are grown. I don't keep rams because my water is too hard but I love the way they look. I have read that they can become territorial so that may be something you will need to watch as they mature.