Why do goldfish jump out of their tank?

Written by jenny green | 13/05/2017
Why do goldfish jump out of their tank?
Goldfish tank lids should let in air. (Seiya Kawamoto/Lifesize/Getty Images)

Goldfish --attractive, coldwater fish with simple needs-- are easy to care for, but sometimes cause distress by trying to jump out of their tanks. Goldfish escape bids can be caused by their excitement about other real or imaginary goldfish, discomfort due to poor tank conditions, or irritation from parasites. Owners shouldn't give up hope too soon if their fish have succeeded in leaving their tanks: reviving apparently lifeless goldfish is sometimes possible.


Goldfish sometimes leap from their tanks as a reaction to other fish. When tank water warms up in spring or summer, goldfish can enter a breeding phase. Male goldfish become very active and start chasing females around the tank, sometimes accidentally jumping right out of it. Some experts believe goldfish can also leave their tanks because they've seen their reflection in the glass and think it's another goldfish. As social fish, they tend to swim towards other goldfish where they feel safer.

Tank conditions

Goldfish try to leave water that feels uncomfortable. Excreting a lot of waste, they need frequent water changes to prevent excess ammonia, which burns their skin and gills. Uneaten food also produces ammonia as it rots. At first, goldfish become more active as they try to leave the water, then they become lethargic and sick. Tank water that's too warm is also uncomfortable for goldfish. The water temperature should be between 18 and 24 degrees Celsius (65 and 75 degrees Fahrenheit). Never place goldfish tanks in direct sunlight.


Goldfish can suffer from parasites that irritate their skin and cause them to swim erratically and rub themselves against objects. In an effort to escape discomfort, they may accidentally jump out of their tanks. Other symptoms of parasite infection are struggling to breathe and spots, dusting, or other changes in their coats. Parasites include flukes, tiny organisms called protazoa, lice and anchor worms. Treatment involves dosing the whole tank with an appropriate, vet-prescribed medication, replacing the tank's carbon filter, and regular water changes.

Prevention and care

Maintaining suitable water conditions and installing barriers helps prevent goldfish jumping out of their tanks. There should be a gap between the water level and the top of the tank, measuring at least the length of the longest fish in the tank. Covering tanks with a light, permeable screen also helps prevent escapees. Replace one third of the tank water every week with clean water that has been left to stand for two or three days. Goldfish bowls are rarely large enough to provide healthy living conditions, so always keep fish in an aquarium tank. Goldfish can survive a surprisingly long time out of water. If you find your fish on the floor and apparently lifeless, try returning him to the tank in cupped hands and moving him gently through the water.

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