I don't know if you can or not but I don't, I use a small sieve and empty them through it over the sink to remove the water. You do not know what else is within the water so that's why I don't.
definatly don't put the water from the bag into your tank . just empty the bag contents into your net and pour water over the top of the worms, then put them in the tank.. the water is really dirty, and would just polute your tank!