In 1878, Rear-Admiral Daniel Ammon brought the first tropical fish from the Far East to the United States which led to a decline in the popularity of goldfish. In the early 20th century, aeration, as well as particulate and charcoal filtration was introduced. The undergravel filter was introduced in the 1950s. By this time, the old idea of the balanced aquarium was viewed as unattainable and unnecessary by many people in the aquarium hobby, but it made a comeback at the end of the 20th Century with the rising popularity of the planted tank.