Fish are the oldest known vertebrates, inhabiting almost all aquatic environments on earth, from freshwater rivers and lakes to brackish seas and oceans. There are about 32,000 known species of fish in existence, with two-thirds of these living in the oceans and the remainder inhabiting various types of freshwater.

Crucian carp, another common freshwater fish, are omnivorous and have a varied diet that includes both animal and plant-based foods. They feed on a variety of items, including branches and horns, copepods, moss worms, rotifers, freshwater shell vegetables, clams, mosquito larvae, and shrimp.

They also enjoy plant scraps and stems, leaves, buds, fruits of water plants, diatoms, filamentous algae, and other aquatic vegetation.

Grass carp, as their name suggests, are primarily herbivorous, but will also eat non-vegetarian foods such as earthworms and dragonflies. These fish enjoy living in groups and are typically found in rivers and lakes in plain areas.

They are fast-growing and have a delicious taste, which has led to their widespread cultivation.

One key difference between freshwater fish and sea fish is their appearance. Sea fish often have more vibrant colors, while freshwater fish tend to be more subdued.

Additionally, the gradient color range of sea fish is typically larger than that of freshwater fish. Sea fish scales are also finer and denser, while freshwater fish scales are larger and harder. When living, freshwater fish may emit a muddy smell, whereas sea fish often have a distinctive fishy smell.

Another difference between these two types of fish is their shape. Sea fish come in a wider variety of shapes and sizes than freshwater fish. Additionally, the flesh of cooked sea fish may clump or form stripes, while freshwater fish flesh is more likely to fall apart.

Fish are a diverse and adaptable group of aquatic animals that have colonized nearly every aquatic environment on earth. Freshwater fish and sea fish each have unique characteristics that make them well-suited to their respective environments.

While freshwater fish tend to have less vibrant colors and denser scales than sea fish, they are an important source of nutrition and a popular food source for people all over the world.