There are some recommended disinfectants, such as Oxyfresh Gel' out on the market. Some people use bleach in their wash water. I don't, I have heard that even the fumes can be toxic to these little guys. This is a list that I found of birds that can be housed together. Of course there may be personality conflicts depending on the personality of the individual bird.
Birds have different personalities, just like humans.
During breeding season, most of these birds, defend only their nest area. For comments and suggestions, please E-mail me.