The Difference Between Saltwater and Freshwater Fish
Freshwater and saltwater fish have a number of physiological differences stemming from their environments. These differences mean that you must take different measures when keeping fresh- or saltwater aquariums. Take these differences into consideration when deciding which type of fish to keep.
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Salinity
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The most obvious difference between freshwater and saltwater fish is habitat; freshwater fish live in lakes and rivers with fresh water, while saltwater fish live in oceans and seas with salt water. This difference is really the key to all other differences between the two types of fish. Because of the process of osmosis, which dictates that water flows from areas of low salinity to high salinity, saltwater fish lose water to their environment and constantly have to drink to maintain the balance and remain healthy. Freshwater fish, in contrast, have more salt in their bodies than in the surrounding water. They do not have to drink, but rather absorb water through their cells.
Sensitivity
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The environments that freshwater and saltwater fish come from also have an effect on the fish's adaptability and sensitivity to environmental changes. Freshwater environments are more susceptible to factors like fluctuating water levels, differences in water clarity and oxygenation levels, and temperature changes. Thus, freshwater fish are built to withstand these changes. Saltwater environments are not prone to such drastic changes, so saltwater fish are less able to handle them.
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Raising
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Because of this increased sensitivity, saltwater fish are difficult to raise commercially. For this reason, most saltwater fish purchased for aquariums have been caught in the wild, while freshwater fish are typically farmed. This is the main reason why saltwater fish tend to be more expensive than freshwater fish.
In Aquariums
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Most people who keep fish begin with the freshwater variety because these fish are hardier and therefore easier to keep alive in an aquarium. If you decide to switch to saltwater fish, keep in mind that some saltwater species are tougher than others. The most important factor in keeping saltwater fish alive is specific gravity, or the amount of salt in the water. This level varies for different fish, making saltwater aquariums much more complex to maintain than freshwater aquariums.
Equipment
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Most aquarium equipment is designed to work equally well for fresh and salt water. This includes heaters, filters and aerators. Additional equipment that may be needed for saltwater setups include sea-salt mix, special gravel made from crushed coral and a hydrometer, which measures the specific gravity in an aquarium.
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References
- Photo Credit fish image by JASON WINTER from Fotolia.com
