Silver in a fish tank

Can I put silver coins in my fish tank without hurting my fish or poluting the water

Here is something I found at

The danger associated with putting coins in your fish tank is dependant on the type of tank you are running (Salt or Fresh water) the coin itself and the species of fish in the tank.

For fresh water systems, placing a few silver coins in the tank will not hurt the fish but stay away from pennies and anything else that will corrode in oxigenated water. I have seen more than one hand made aquarium ornamental structure fall apart because it was held together with mild steel bolts. In anycase, your regular tank maintenance to remove nitrates (by changing the water) will ensure that any metals dissolved will remain low in concentration.

For Salt water systems, the answer is No, Coins are not acceptable additions to the aquarium and it will harm your fish.