Swallowing a stone will not sink a goldfish and they are not likely to do that anyway. They know what is food and what is not. The reason a fish sinks to the bottom is because it is very sick. I would guess the fish is probably dying or dead through being kept in bad conditions. The basic rules for keeping fish well and healthy are :- "1 inch of fish needs a minimum of 1 gallon of water , a permanently running cycled filter and at least 50% of its water changed every week". If you didn't comply with any of the above that is what is wrong with your fish.
Sand is an insoluble substance that sinks to the bottom.
Well yes that is a hard thing to find out because fish don't have eyelids but if a goldfish is upside down or sideways or just sinks to the bottom its dead but if it just pausesit just means its taking a little snooze!
Not Yassine JR
Displaction
It dies
Sediments
It sinks to the bottom and the crabs eat it.
forms a sediment when it sinks to the bottom of a liquid.
Sinks to the bottom, very rapidly.
seamen
because it is heavier so it sinks to the bottom ~berkles
The density of the material is greater than the density of water if it sinks to the bottom of the container when placed in water.