Don't know about the aspirin thing, but I do know about salt. Hauled several millions shiners around the country. Salt relieves stress from overcrowding and promotes slime growth. Slime is the fishes auto immune system. When they throw their slime coat they will shed their scales very quickly and die. Had 12 tanks on the truck, each holding 90 gallons of water. Before loading I put 2 cups of mixing salt in each tank. Must be mixing salt. Iodized table salt in quantity will kill shiners. Each tank held 125# of shiners for a 48 hour trip. Fish farmers put from 50 to 100 pounds of salt in a 1000 gallon vat when they bring shiners into the shed. Then they flush them every day, sometimes twice, and add 50 pounds of salt. Best insurance a fish farmer has. Very rarely lost any fish unless I had an oxygen issue.