I Have Two Goldfish In A 5gallon Tank. Their Fins Are Droopy And They Just Floating/doing Nothing. Also Everytime I Walk Into The Room Their Fins Perk Up And They Start Swimming. When I Go Out Of The Room, They Go Into Lazy Mode Again. They Are Eating Normal And I Do A 30% Water Change Everyweek. I Also Have An Airstone In, But No Filter. What Is Happening?