My brother (who lives away) had a fancy goldfish in a 10 gallon tank with a filter but no chemical media, it was just a sponge in the filter tray and yesterday he upgraded him to a 20 gallon long. He said added chemical media of charcoal and something else I can’t recall the name of to a filter bag and popped it into the filter tray along with the same sponges from the 10 gallon, same deco and substrate. He sent me a message this morning saying the 20 gallon water is misty/cloudy. He’s got no API kit so he can’t test the water. Is this normal or something else?