HELP. Goldfish swallowed something? or?

[Absolute2purity]

How can i know if my goldfish swallowed something like a lil piece of gravel? i had a plastic/glass thermometer break in the aquarium like a yr and a half ago when i first set up my 75 gallon? i have a goldfish only 1 in tank. parameters ammon- 0 nitrite-0 nitrate 40-80 prbly 60. hes fine most of the day and happy but does this strange lil shimmy gesture to me but not anytime else. only to me. idk if its social gesture or a cry for help especially when hes happy fine and interactive most of day. idk whats wrong and im concerned. trying to get ahold of vets and expertise places as soon as possible. i thought it was flukes for 6 days but been on prazi for 5 days now. it did nothing first 4 days but this morning he was totally fine and happy i sat w him since 5 am to 11 am and he was fine happy and normally interactive like some kind of miracle but he was flashing for 5 days and was lethargic 3 times yesterday. im very confused and concerned. hes 10 inch comet goldfish. a vet said to watch what he eats and how he poops next day or 2. so will he be ok??

[Autumnsky]

Water parameters???

What would make you think it swallowed something?

If the mouth is stuck open? If something is in the mouth you can see. You would be able to hold the fish and remove a pebble. More info if you think it is.

But there shouldn't be mouth sized gravel, GF are always sucking stuf off stones and spitting them out. I had a GF in my pond have a stuck pebble and survived to live on after the pebble was removed. It was introduced by a water lily with gravel on top of the soil in the basket.

It could be a water quality issue.