No wonder Goldfish have been nicknamed “Water Puppies” 🥰 Goldfish are very enjoyable once you have the correct set up for them! Despite beliefs that they can live in fish bowls, fancy goldfish grow to be about 6-8”. Common goldfish get even bigger, maxing out to about 10” in aquariums. We highly recommend at least 20 gallons for juvenile goldfish and 35 gallons for a single adult goldfish. If you have more goldfish in the aquarium then go bigger. This is due to how messy goldfish are, they make a lot more waste than some other commonly kept fish and therefore need a larger water volume. Maintenance on your goldfish aquarium is also very important! Since they are messy, we recommend water changes of about 30-50% every week or at the very least every two weeks.