3lbs per 180 gallons will not cause the rays any irritation at all. We dose 3-4lbs per 100 gallons quite often when we see problems. Also you cant use a hyrdrometer to test for water softener salt in freshwater. You need a freshwater pond salt test kit. 3-4 lbs per 100 gallons will give you a 3.0-4.0 salt reading on these types of tests. The redness on belly if more then likely from Ammonia or nitrates from shipping or you water in your tank. 2 days in shipping is your likely cause ammonia etc.
could you be more specific?