Tank Swap

I am thinking about switching up some of my tanks. I have a 55 gallon saltwater a 10 gallon freshwater and a 20 gallon tank that is not in use. I want to put all my freshwater fish from the ten gallon into the 20 gallon.Then I want to put my saltwater fish from the 55 gallon into the 10 gallon.Then I want to go buy and buy a snowflake eel and put it in my 55 gallon. I want to know if this is a good idea.