Why does my Goldfish keeps opening mouth at top of tank?

Answer 1

Because he's either dead, or stupid...no, you're stupid about fish...

the real problem is either a fungal infection sealing its mouth or something similar

things to try to help fix:

--->you can try using anti-fungal medicine such as Fungus Eliminator as recommended on this site Veterinarian Help & Pet Health Questions > Our Goldfish seems that the mouth is sealed shut with some ... > Goldfish

----other more crude and not recommended way is to very carefully, probably by a vet, surgicly open the mouth with a procedure found at: Goldfish

... for those without the time to search the page, here is the excerpt

7. Fused Mouth!! Yes sometimes a) a fungus, or b) eating too much hard food (which will scrape the skin on a goldfish's mouth) will cause the fish's mouth to fuse -- partially or FULLY shut !! It will easily cause death, because the fish cannot breathe! (they bring the water through their mouths and it filters oxygen through the gills that's how they breathe. If their mouths are fused shut, they die). This is what I have done to save them and it must be done CAREFULLY and respectfully. Sterilize and then wash off an exacto or small sharp knife, get some salt (table, kosher or aquarium). Take the afflicted fish out of the water, secure it gently and carefully with gloved hands or something just as gentle, and cut open its mouth (to its original, natural size) along the natural mouth lines. You can determine the natural mouth lines by gently squeezing its jaws to open the mouth if it is capable of opening, even a little bit. Then when you have cut open the mouth to its natural size, rub some salt on it, to keep the cut from healing. If you are lucky, you will be able to do this on the first try. Once you finish this operation, observe the fish carefully for the next 24 to 48 hours sometimes the mouth closes up again, and you have to re-cut and re-salt it. Ugh! This is the only thing I find that works. I was hurting, the fish were hurting, but it had to be done (or they would die) Once they totally healed from this, their lives were saved and their little mouths were able to open fully again! Miss Moustache, and Mr Bee all had to go through this, sometimes more than once, when they were very small fish. So, if you keep the hard food away from your fish, they will run less risk of fused mouth.

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Answer 2

It is a normal goldfish action, provided that it's not in a fast continuous motion which can be described as looking like a pant. If they are 'panting' then you may need to do a 50% water change, and also take a close look at their gills to see if they have any sort of inflammation or infection as this can mean gill flukes.

Answer 3

This is common for some fish to do as a type of breathing. A fish that does this naturally will look calm and open the mouth in a similar repeat fashion.

If your fish does not look relaxed and looks like it is 'panting' or 'gasping' intermittently this can be a sign of infection, low oxygen levels, high ammonia levels, something stuck in the mouth of the fish, or just that your fish likes to exercise its mouth.

Answer 4

To breath