It is a way of freeing up our energy, of subconsciously listening for someone to come in. Yes, but you have to watch out for electromagnetic fields. For instance, we don't want too many electric appliances on at night when we are sleeping. Yes, fish and animals, in fact, all our pets and anything that is alive, including plants are very good because they have energy and stimulate the chi. Fish are also considered lucky because of the water.
Water is equated with wealth.
Fish can bring in money. That is why you will often see fish ponds at the front of Chinese restaurants. There is a large aquarium at a Chinese laundry I go to when I am in New York. In addition, many times there will be eight red fish and one black fish. Nine is the ultimate yang number.