There may be five reasons why goldfish always float to the surface:

1. The oxygen content in the water is too low: it makes it difficult for goldfish to breathe, so they float to the surface to breathe.

2. Indigestion: It may be that the owner feeds too much, causing the goldfish to eat too much and suffer from indigestion, causing it to float to the surface to breathe and digest.

3. Weather reasons: It may be that the weather is relatively hot or it is about to rain.

4. The water quality is too poor: The water contains too much residue and dirt, which causes peculiar smell and odor in the water, affecting the growth environment of goldfish, so goldfish will float to the surface.

5. Food is on the water: When food is floating on the water, the goldfish swims to the surface to eat.