Has anyone left copper in their tank for a long period of time at 1.5 strength, reason is I been fighting ick for 3 years no kidding did copper for 30 days at 2.5 strength in Feb and again they are back. It's like the strain is resilient. Left copper in the tank after water change of 30% the last 32 months and no sign of ick or what ever parasite it is. Apparently copper must be totally out now since its back. Thanks for your time, Carl