Decoding goldfish behavior

If you keep pet goldfish, you have almost certainly spent many hours watching them go about their daily lives, interacting with their surroundings and each other, and doing all of the normal things that goldfish do!

But have you ever watched your goldfish swimming around and wondered exactly why they are doing what they are doing, or what their behavior means? Many of us have!

Goldfish are generally thought of as being fairly simple creatures, and the different behaviors that they exhibit are not difficult to interpret, if you know what you are looking for. Read on to learn about how to decode some of the most common pet goldfish behaviors.

Understand how your goldfish behaves

Socialization and taming

Goldfish are fairly social fish, and are also credited with the ability to learn by association. Unless they are in competition with each other for food, even goldfish of different sizes and ages will rarely behave aggressively towards each other, and will come to recognize the other fish in their tank over time.

Goldfish also become used to the presence of the people that feed them and that they see every day. They will soon learn when feeding time is and that, if someone approaches, they might soon be fed! Goldfish will often come to the top of the tank when someone approaches or follow the progress of a hand moving on the other side of the glass.


Goldfish love to dig about in the substrate of the tank! This is normal goldfish behavior and one that you will be able to observe quite often. There are elements of both foraging for food scraps and making their mark on their environment involved with this activity, and as grazing fish, goldfish do like to constantly have something to nibble on!

Goldfish will also often eat the plants within their tank, and this behavior can be viewed in the same way as any other grazing animal, such as a horse or a cow, whose metabolism is constantly in motion.


Goldfish are not always among the fastest moving fish, but occasionally they will show quite a turn of speed! If your goldfish are chasing each other around the tank, this is sometimes the lead up to mating and generally not cause for concern.

However, if your tank is overcrowded or your fish are in competition over food, your goldfish may become stressed and chase each other off in competition for resources.

Hovering at the tank’s surface

Goldfish tend to use the full depth of their tanks from top to bottom, unlike some species that generally show a marked preference for a certain area of the tank. However, goldfish will congregate near to the top of the tank if they are expecting food or if the oxygen levels in the tank are low.

If your fish are gulping air at the surface of the tank or are regularly breaking the surface of the water, check your water quality and aeration for any problems.

35 thoughts on “Decoding goldfish behavior”

  1. My big fan tail fish is benign chased by 3/4 smaller sized fan tail fish for most of the day today and the day before and not sure why. It’s like there going for the bottom of the tail on my fish and the tubing up and piken the sides of it. I have 15 fish and its only 3/4 that do it rest of them dont bother. Any ideas to why there doing it would be great.

    • Hi Kassandra – thanks for your message. Are you saying that you have 15 goldfish? Or goldfish with other types of fish too? Are they in a pond?

      If your fish aren’t in a pond or an extremely large tank, it’s possible that over-stocking (likely leading to poor water quality) could be a factor in your fish’s behaviour.

      • Hi all, turns out my goldfish was attack by this thick white layer. So quick that thing grow it was all over its body, (pictorial fin, tails, head, mouth.) I just placed him in a salt bath and melafix for 24h now, the body seem clearer without that white layer anymore, but it seem passive with little move, rest at the bottom of the tank . It wont eat anything either. What should i do ….am soo saddd

  2. My daughter won 2 goldfish at a fair a year and a half ago. We had them in a 1 1/2 gallon cylinder tank, but a week ago moved them to a 10-gallon with a more powerful filter (creates more current in the water) and led light. They hide at the back bottom corner anytime a light is on (the light in their tank or the light in the room) or if they notice one of us near the tank. They also are not eating nearly as much as they did in the old tank. A friend who is really into fish keeping came over and set up the new tank for us and she is stumped. We’ve checked pH, ammonia, nitrite, and nitrate levels and done a 1/4 water change. Any thoughts?

    • Hi Ellen. Are there other objects such as plants or ornaments in the tank? While you don’t want to add too many – every object takes up valuable water space, especially in a 10 gallon – goldfish do like to have somewhere to hide rather than being out in the open all the time.

  3. My goldfish gets so excited when she sees me. Its almost as if she wants me to pick her up and cuddle her and its EVERY time I’m working on the surface where her tank is. I feel I have to get out of her sight to let her rest. Is this normal?

    • Hi Cheryl, thanks for your comment. This does sound totally normal! Goldfish can get to recognise people and they definitely associate people with being fed. Perhaps your goldfish is hoping for some food every time she sees you?

  4. I have a small garden pond which had two goldfish. One was taken a few weeks ago.bive just replaced with a new goldfish and the original one is chasing it everywhere. No aggression, just shadowing. Is this normal?

    • This seems normal yes, goldfish are very social fish and will naturally attempt to school as long as there are more than one of them.

  5. Hi, we have 4 x goldfish and today noticed that 3 are chasing 1 fit a good portion of the day, I suspect he is a she and possibly trying to mate,
    Question: is mating during a particular time of year and what are the chances of this fish become pregnant and producing fish eggs which new born surviving?


    • Hi scott, thanks for your comment,

      This sounds like typical spawning behaviour.
      Goldfish will spawn when they are in “condition” and this can be caused by a few different things, good food, stability, clean water, drop or rise in temperature and a few many other factors.
      If you keep your fish in an outdoor pond, then typically they will spawn in late spring or early summer, and then again in autumn, (if you live in a temperate climate.)

      Goldfish also reproduce externally, which means she does not become pregnant, but will release eggs and the male will fertilise them, outside of her body.

      Goldfish release thousands of eggs when they spawn, the likelihood of them surviving depends on the ammount of cover provided in their home.

  6. I have a short video of my goldfish making noises when he sees me in the room and wants food. How may I post or send it to you?

  7. One of my goldfish has been nibbling another underneath its tail. Could he be eating waste matter from the fish?

    • Sometimes, especially fancy goldfish when kept in tanks, can bully each other a little, it sounds like the goldfish are maybe establishing a little dominance.
      As they do tend to nibble each others undersides when trying to assert themselves.

      If the water is cooler, the fish receive enough food, and there is enough cover and space for them to get away from each other, this should stop.

  8. Hello!
    Goldfish keeper of 1year now.
    I have a question about my Fancy goldfish Jaws.
    We recently moved 3 fancy goldfish over from a 30Gal to a 75Gal (yes I know it was a little squishy, that’s why we got a bigger tank). It’s about 3weeks now and Jaws is obsessed with swimming to the top left corner surface of the tank where my sponge filter bubbles come up from, where the pathos plants are and is close to the filter output.
    He literally just swims towards it for HOURS. He doesn’t eat the pathos, just swims towards the bubbles and towards the water output from the filter.
    He’s never done this in the 30Gal, the other two goldfish don’t do this, only him. His dorsal fin is out of the water when he does this and his face is almost breaking the surface. He does this after water changes and water parameters are good.
    I think my fish is broken…. All feedback welcome and appreciated.

    • Hi janelle, we hope you have managed to find out or fix whatever is causing this,
      My guess is there isn’t enough oxygen in the water, and it seems to be affecting him more than others potentially.

      additionally he could be stressed, and is trying to get to the corner to avoid the source of the stress.

      I would suggest adding more plants or decor, and a couple air stones if you haven’t already by now.

      hope this helps

  9. I have a big 20cm comet and a 15cm black moor in a 200L tank. There’s only two small orandas in there with them. These two aggressively chase And nudge each other every evening. But there’s no nipping or biting. It can be quite stressful to watch as they get splashy sometimes. I worry they’re stressing each other out but they seem fine afterwards and it’s been happening for a while now. Should I be concerned? I hope they’re just playing.

    • Hi Teigan, thanks for your comment, we hope you were able to find out what it was by now.

      It isnt in the nature of a fish to play with each other, it is more of a mammal thing to do that.

      It sounds to me like your goldfish are attempting to spawn, it is a completely natural process and means your goldfish are actually in good health and are happy.

      The chasing can be stressful for them sometimes, but it is necessary to get the eggs out of the female, as sometimes they can become clogged and this can be fatal.

      If you are concerned then maybe provide more plants and cover for them, or expand their pond/tank size. but this sounds like a completely natural occurrence.
      hope this helps.

  10. Hi… I recently purchased my two large goldfish and they were extremely playful with each. I noticed recently only during feeding time the male goldfish get a little aggressive and keeps knocking the female one. What should I do???

    • Hi Ronell, thanks for the comment. As long as the male goldfish isn’t being aggressive all the time, or knocking hard enough to cause injury, then this doesn’t sound too concerning. Though obviously it would be good to stop all aggression if possible.

      If it’s only happening at feeding time and they’re fighting over food then have you tried adding food at opposite ends of the tank to see whether you can encourage them to eat separately?

  11. Hi please help!! I just got this goldfish about 3 weeks ago and everything was great but all the sudden he seems not him self, just sitting in the corner or at the bottom laying on the gravel he has a fee white spots on his fins that have gotten worse but i have treated for ich and fin rot because i cant tell for sure what it is, he also just kind of floats lazily like hes bored but something is definitely wrong please some one help me! I dont want to lose him! All water readings are great no ammonia no nitrite no nitrate and ph is a little high at 8.0 but always has been so what should i do? He is also flashing occasionally

    • We hope you were able to treat your goldfish by now,

      Fin rot is characterised by fluffy, white fungus on the fins, and the decomposition of the tail and fin membrane.

      White spot will typically live on the body of the fish, but can live on the fins too, the flashing makes me think that it is white spot as the fishes skin is irritated.

      A pH of 8 is also okay, goldfish are heavily adaptable, the only thing that would cause stress is if that pH jumped up and down all the time, as log as it remains stable, it should be fine.

      here is a page we have on whitespot:

      hopefully this helps

  12. I’ve read that goldfish can become under stimulated and depressed. My common goldfish (female) lives in a 36 gallon tank. She is about 2-3 inches in length now. The tank is cycled and stable. Should I add a second goldfish to this aquarium, or would she be just fine as an only fish? Do goldfish need companions?

    • Hi Julie, thanks for your comment,
      ideally it would be good to get another goldfish, as they are naturally schooling fish and prefer to be with their own kind. just be sure that you pick out fish of a similar size and ones that are healthy and show no signs of illness.

      We recommend quarantining any new fish if possible for around a week before adding them to the tank, just to eliminate the threat of disease spreading.
      Also be aware that for 2 adult goldfish, 36 gallons will be too small, since they will grow around 7 inches or more.
      But you will get plenty of time from them in a 36 gallon, it may just need upgrading a year or so down the line.

      hope this helps 🙂

  13. Hello, I have 2 goldfish ( bought at the same time in June ) Yesterday, I changed the water in the fish tank, today one of the fish ( bigger ) started chasing my other fish ( smaller ) more then usual. I tried to distract them with food, but they haven’t noticed, which is weird since they love food. My smaller fish was sick 2 weeks ago, i thought it got better but now I’m not sure. Do you have any advice ?

    • Hi Koda, thanks for your comment,

      if your goldfish are mature, then this is possibly spawning behaviour, water changes often trigger breeding condition in fish and can make them hormonal, chasing is how they court each other.
      For real signs of aggression look at the fins for tearing or nipping, the skin/scales for any marks or bruises and the top of the eyes for any white marks, spawning usually wont cause any damage of this type, but aggression will, this is a good way to tell if its fighting or spawning.

      If you are concerned, then cool down the temperature of your tank, goldfish are more aggressive and boisterous in warmer water, you can also add more plants and cover, and feed things like algae wafers, green beans and boiled veg, which take a long time to eat, keeping the fish occupied.

      hope this helps

  14. I had a goldfish a shabumkin and a fantail . The fantail died so we bought another to replace it. But when we put it in with the other 2 they wouldnt leave it alone and the next day I found it dead. Now the shabumkin is chasing the goldfish in circles and pushing it up from under its back end. They are about 18 month old and approx 5 inch in length . They have never behaved like this before.
    Also some of the goldfish scales are turning white.

    • Hi Anita, thank you for your comment,
      fish can become irritable when conditions are off and they are uncomfortable, we would ask you to test your water to see if it is clean, perhaps there has been a drop in pH or surge in ammonia levels, test the temperature too, perhaps it has become too warm and they are displaying aggression due to being under discomfort.

      If the tank seems fine, perhaps this was spawning behaviour, as it sounds like they are reaching that age, but keep a close eye on them for any decline in health, it may be disease what has killed the fantail

      it is very unusual for goldfish to kill each other like this, but we would highly suggest against getting another fantail, comet goldfish and shubunkins are what we call common goldfish varieties, and they do not house well with fantails or any other fancy goldfish, if you do get another fish, get another common goldfish or shubunkin.

      Test the water, do a water change if necessary and keep a close eye on them.
      hope this helps

  15. I have a planted tank with no substrate, with plants stuck in rocks and whatnot, one of my goldfish (comet) is constantly sitting on the bottom of the tank, dorsal fin up and only comes up when it’s feeding time and when that happens she is erratically moving her pectoral fins but not darting around, and once the food is gone, down to the bottom she goes. and just stays there, hiding behind the rocks. Water changes and different types of foods have no effect on her behavior. Pretty sure this is not normal, any ideas of what could cause this?


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