Here's why:
* Similar appearances: Both fat and pregnant fish can have a rounder, fuller belly. This makes it difficult to distinguish between the two based on visual cues alone.
* Internal differences: The reason for the round belly is different. A fat fish has extra fat reserves stored in its abdomen. A pregnant fish has developing eggs in her ovary.
* Species variations: Different fish species have different body shapes and reproductive cycles, making it even more difficult to generalize about pregnancy.
If you are concerned about a fish's health, it's best to consult a qualified fish veterinarian or a knowledgeable aquarist for advice. They can assess the fish's condition and determine the cause of its rounded belly.