The Goldfish using a one-way flow respiratory system. The gills are located inside their mouth and on the side of their head. The water flows into their mouth and passes over the filaments in the gills and out through the gills slits on the side of its head. This way the water is all moving the same way. In order to get the oxygen from the water into their bloodstream. This happens over a large surface of capillary membranes, located in the fillaments of the gills.
Goldfish are a fresh water fish, in the Cyprinidae family and are native to East Asia. They range from a olive green color to a gold/orange color. They grow to about 120 to 220 mm.`