Goldfish are often kept in small aquariums with a volume of fewer than a gallon of water. Although these little creatures are quite hardy, they need an aquarium that can hold at least 5 gallons of water for a comfortable life. The fact is that these fish produce a huge amount of waste, so they need a very powerful filtration system in their aquarium. And most importantly, goldfish can grow up to about 10-12 inches in length and live up to 20+ years. Few people suspect this since these fragile creatures often die at a young age, without even having enough time to grow up. And it’s all because they are in the wrong aquarium.