Is 0.2% silver impregnated charcoal in a biological filter toxic for goldfish?

In my biological filter, 200 grams wood charcoal is required. I have procured a kg of charcoal from an "Aquaguard" water purifier service center. On the packet, it is written, "BACTERIOSTATIC ACTIVATED CARBON, 0.2% SILVER IMPREGNATED." I cannot find any normal charcoal which does not contain any silver. So I am worried that if the silver will cause any toxicity to my goldfishes. Please can anyone tell me whether silver is toxic to my fishes? Thanks a lot in advance for your help. My tank is 500 litres.