This hasn't been mentioned but it could help a lot. I know that copper leaches in the water MUCH more when you use warm/hot water from your tap.. I believe our water heater adds copper to the water as well. If you have this problem, just fill a large tub with ice cold water, and let it sit until it reaches room temperature, or heat until it is the same temp as your tank water.
From a shrimp website:
"Most important in water is ensuring that chlorine, chloramine and heavy metals are removed with dechlorinators prior to adding to the tank. With their increased sensitivity to heavy metals shrimp are more susceptible to leached ions from hot water systems in which water contact with copper pipes is longer. It is highly recommended not to use any hot tap water when performing water changes."