I am helping a guy setup a display pond at work thats about 100 gallons. I thought that if it was filtered with an XP3 or something equivelent that the carbon could help reduce the risk posed to the fish> (kids are going to throw coins in no matter what). I think they just want some goldfish of some sort in there. What are other fish that could work well in a small pond like that? keep in mind this is in a very public place....any other advice would be great! thanks in advance.