When you have an employer group health plan and want to apply for Medicare, the work status of the policy holder (you or your spouse) affects whether or not you will be in a Coordination of Benefits period.
Copper is an excellent treatment for saltwater ich or marine velvet disease, but it can be toxic and stressful to fish. Of course, using it is much better than letting a fish die from velvet, but it should never be used in a tank with healthy fish. Improper nutrition is also a commonly overlooked stressor of fish.
Even tiny amounts of heavy metals may harm fish. It has been suggested that fish should not be exposed long-term to more than 30 micrograms per litre of lead or iron, or to more than 15 micrograms per litre of copper. (1 microgram per Litre is equivalent to 1 part in 1,000,000,000.)