There are many types of fish. Scientists have quantified around 27,900 different species, both freshwater and saltwater . But what is the difference between freshwater fish and saltwater fish? They all live in the aquatic environment, they have a brain that is protected by a cranial box, most are vertebrates that protect the spinal cord.
The differences are found in the environment, whether salty or sweet, in which they live. These are very important if our intention is to buy or compose an aquarium. Not all fish will be able to survive in an aquarium if we cannot make it suitable for their life characteristics.
Differences between freshwater and saltwater fish
One of the main differences between these fresh and salt water fish is the adaptation to the environment of their own kidney. Saltwater fish have not developed kidney glomeruli that cause the water they eat to pass through their gills. These glomeruli are capable of eliminating water in abundance and absorbing salts , something that saltwater fish have not been able to adapt, or at least, they do not need.
Freshwater fish have evolved cells that make them capable of absorbing salts such as chloride and sodium to reach their blood. This means that freshwater fish have developed a system that allows them to solve the loss of salts and gain abundance of water.
However, saltwater fish, living in an environment with a high concentration of salt, have not needed to develop capacities to adapt and, through osmosis, they are able to expel body fluids and recover the water by drinking.
For this reason, fish from a salty environment do need to drink water, something that freshwater fish do not require.
There are some exceptions like salmon. This type of fish is considered an anadromous fish as it is able to adapt to both livelihoods. When salmon hatch, they do so in fresh water, but when they grow and develop they have to migrate to salt water.
To have an aquarium we must be clear that saltwater fish are much more difficult to conserve since adapting their environment is more complicated. The temperature of the water must always be controlled with a good pH and they will need much more space.
However, freshwater fish will make us have a cheaper aquarium, although we will need that the capacity does not lower than 60 liters and install a filter and a screen.
