Why Do Goldfish Swim At Top Of Tank?

LoL Most fish don't have the ability to breathe from t heir mouths like one person said... Instead they come to the surface where there is more oxygen. Oxygen enters the tank from the surface and only if there is good waterflow can get to the bottom.

Also as someone else mentioned you should see if they'll eat because they may just be skimming the surface for f ood particles. Keep in mind that if they eat it doesn't eliminate any factors but decreases the chances.

Many times it's swim bladder disease or their stomache applying pressure to their swim bladder. I would say if you have a water filter already it's probably not oxygen as fish use VERY LITTLE oxygen and there is generally quite a lot available in even still water. Also it's not always easy to guess which fish need more and which need less but fish from lakes generally need less than fish from rivers and fish from rivers need less than fish from streams...

First what kind of fish do you have? Some prefer different levels of the tank. If there is not enough oxygen in the water from ammonia, ph and nitrate levels a fish will gasp for air at the surface.

It depends. Were they like that when you first got them? If so then its probably normal.

Well it could be because there are to many fish in the tank, wrong temperature, feeding them to much, feeding them to much.  Or they could be killing each other

Their probably getting air, sucking it in their mouthes, and it goes through their gills, this is for emergency, when there is not enough air in the tank.

Either not much oxygen is getting to the rest of the tank, or the water is too dirtyso there gasping for air at the top.

Your fish are at the top of the tank to get oxygen.In a tank there is only a limited amount of oxygen.When oxygen is finished the fish come on top and breathe from their mouth rather than the gills.Thats why we do not find any fish in the top layer of water in seas or rivers.Seas and rivers are always moving.They have sufficient oxygen in it.I suggest you keep an oxygen motor.

You have a lack of oxygen in the tank. Firstly change 40% of your water. This will help in the short term. You should think about planting your tank, plants release oxygen into the water so your fish'll benefit. Next you should move your filter so the flow breaks the top of the water surface. It's a myth that airstones add oxygen as all they do is break the surface to MIX fresh air into the tank. So simply using your filter flow will do the same thing. Good luck :)

It is most likely the way you feed them. If you are feeding them some sort of flake or any floating food they will sit and the top of the water when they are hungry. My Zebra Danios did this also then I started feeding them tubifex worms that stick to the side of the tank so now when they are hungry they all go to the side of the tank where I can still see them.

The Fish Need Oxygen,so they always stay at the top.

They are swimming in the area of the water with the most oxygen.  If the tank has an aerator the fish would be swimming at all depths.

You fish is die