I just remembered a friend of mine has a goldfish tank for her daughter. She is willing to give me some gravel and her old filter media. She changes it every month or 2 and I believe they are activated carbon cartridges. The tank is 2 years old her daughter won the fish at a fair. I asked her if they have ever been sick and she said no. I read that these types of goldfish can carry disease, so I am looking for advice on this. Thanks!