As well as getting water through osmosis, saltwater fish need to purposefully drink water in order to get enough into their systems.
The answer is still no; as they live in water they probably don't take it in as a conscious response to seek out and drink water. Thirst is usually defined as a need or desire to drink water. It is unlikely that fish are responding to such a driving force.
Fishes dont actually drink water, down through the mouth. But obviously they need water, like all living things need to live. They genearally absorb it through there skin (osmosis) same way hormones and nutrients are absorbed in to our blood.
Water flows into their body through osmosis, instead of out. This means they don't generally need to drink – but they do have to pee a lot.
Freshwater fish never drink water because their bodies are saltier than the surrounding water. Osmosis draws water into the fish's body through its skin and gills, unlike saltwater fish, where the water is drawn out of the body. If freshwater fish did drink water they would blow up like balloons.
Municipal/Tap Water
Most municipalities treat drinking water with either chlorine or chloramine for disinfection purposes. Chlorine is extremely toxic to fish and needs to be completely removed before the water comes in contact with fish. Chloramine is chlorine bonded to ammonia, both of which are detrimental to fish.
Ordinary tap water is fine for filling up the aquarium as long as you let it sit for several days before adding fish (the chlorine in the tap water will kill the fish).
While fish do not sleep in the same way that land mammals sleep, most fish do rest. Research shows that fish may reduce their activity and metabolism while remaining alert to danger. Some fish float in place, some wedge themselves into a secure spot in the mud or coral, and some even locate a suitable nest.
Nerves, brain structure, brain chemistry and behaviour – all evidence indicates that, to varying degrees, fish can feel pain, fear and psychological stress.
Freshwater fish will passively intake water from their environment and then, as their insides are saltier than their surroundings, will excrete a diluted urine. Saltwater fish have to drink water more actively and, as their surroundings are saltier than their insides, will expel a more concentrated urine.
Surprisingly, science has found that fish are capable of recognizing their owner's face, even if the owner is standing by the tank with other people. Fish can develop an association between something they like, being fed, with the person who feeds them.
To prevent this from happening, allow the fish bag to float in the aquarium for 10–15 minutes to acclimate them to the water temperature. (If the fish are in a breather bag that allows gas exchange, place the bag on the aquarium lid for about 30–60 minutes.)
How long should I keep my aquarium lights on? To provide animals and plants the lighting they need, 10 to 12 hours a day is sufficient. Installing a timer or purchasing a unit with integrated timing can make lighting easier––just set it and forget it. Keep in mind algae loves light as well.
Toxins. Agricultural runoff, sewage, surface runoff, chemical spills and hazardous waste spills can all potentially lead to water toxicity and fish kill. Some algae species also produce toxins.
Your best bet is to check on your fish as it dries and test it. Look out for it turning firm, feeling completely dry, and yet still pliable. If you see any hints of moisture still on the fish, keep drying. If it falls apart when you bend it to test for how pliable it is, then you have dried it for too long.
Can your pet fish recognize your face? A new study says, Yes, it probably can. Researchers studying archerfish found the fish can tell a familiar human face from dozens of new faces with surprising accuracy.
According to Balcombe, some fish (though certainly not all) do actually enjoy being touched by humans.
The cerebral cortex and limbic system are absent in fish. Cerebral cortex, which is what permits other animals to cry.
Fish living in the deep sea manage to navigate in complete darkness. It's not strictly 'seeing' but fish have rows of pressure-sensitive organs running down each side of their body called the lateral line, which allows them to sense nearby animals from the pressure changes in the water.
Most fish are slightly denser than water, so sink immediately after death. However, like a drowned human, they become more buoyant over time as bacterial decomposition produces gases inside the body. Usually, enough gas builds up in body cavities to make the corpse float, like an inflated balloon.
Fish-keepers sometimes see their pets 'glass surfing' – swimming repeatedly up and down the glass of the tank. This could be the aquatic equivalent of the pacing of a captive tiger that's bored from a lack of stimulation. But the fish could also be stressed from an overcrowded or unfamiliar tank.
The differences in acidity and dissolved oxygen, not to mention all of the fat, proteins, carbohydrates, and other minerals in the milk that might clog the creature's gills, would quickly spell trouble. The animal would likely die within minutes, if not sooner.
Fish/shellfish should go into soup last
The secret of boiling fish is that you mustn't let it boil. It should simmer/poach at a temperature just below boiling point. Fish chefs we've talked to recommend simmering in cooling water.
If you cannot use your tap water and your tank is small (less than 10 gallons), we recommend you try bottled spring water. This is readily available in most grocery stores and can provide excellent water for your fish.