I’m sitting here wondering why the water level in my tank stays pretty consistent even with evaporation possibilities, fish peeing, etc. Click the link to read my post on why my fish tank’s water is evaporating.
The water level never really changes even though fish are obviously peeing and we have twenty fish in our tank so what gives?
Are my fish drinking the equivalent amount that they each pee out? What is going on here well keep reading as there are some differences between saltwater fish and freshwater fish?
I’m going to concentrate solely on freshwater fish here but we will be discussing saltwater fish and their drinking habits in this article. Why saltwater fish drink water it’s a thirsty job
Firstly let’s answer a few questions before getting a little more inclusive
Do Freshwater fish drink water?
Do Freshwater fish get thirsty?
Good questions I’m sure we can agree and with freshwater fish, it’s pretty straightforward
The answer may or may not be surprising
Freshwater fish do not drink water they absorb water via their gills and skin allowing them to stay hydrated & regulate salt & mineral intake this complex mechanism means they never get thirsty.
Water Is Passed Over The Gills
Fish have an impressive way to convert or get oxygen out of water. Freshwater fish take water through their skin and gills.
This is a process known as osmosis not to be confused with reverse osmosis by way of filling our tank water.
Water that is taken in via freshwater fish by their mouths is flushed over the gills. These gills are at the sides of the mouth.
Above the throat so no water gets into the throat. So water comes in and goes over the gills wait what are gills?
Gills are basically blood vessels hundreds of blood vessels and these vessels are called capillaries I know don’t worry I’m all about simplifying things this is not gonna get overly scientific.
Freshwater fish take the water in and the capillaries/vessels take the oxygen out of the water and flush excess water back out.
Osmosis Freshwater Fish Are Saltier Than The Water They Are Living In
Osmosis is the process of the water flowing over the gills and the capillaries dissolving the water and taking the oxygen out.
Oxygen is harder to find underwater there’s in fact some 33 times less oxygen found in water than that found in the air.
So we can all agree these gills are designed perfectly and do a great job. What’s even more impressive is the fact freshwater fish have more salt in their bodies than the water they reside in.
This effectively in laymen’s terms means if freshwater fish don’t get enough salt they will blow up till they explode.
So to combat this problem those amazing gills get to work. Ove each capillary/vessel are specialised cells.
These cells are called Ionocytes and they act as a pup to keep the correct levels of sodium in the fish’s body and obtain homeostasis.
What About Excess Water That’s Absorbed Via Skin?
Fish take on a fair amount of water this is also true of freshwater fish. The skin is very mailable and the membranes are super slimy how slimy click the link and find out. Anyway, the skin is thin enough for water to pass through.
With this in mind, these particular fish have kidneys able to process the water and get the required minerals out including salt.
After this process even more salt is extracted just before the fish pees it’s a fine art that they have perfected.
Freshwater Pee Very Diluted Water
Indeed these type of fish freshwater fish has to take on a fair amount of water to process enough oxygen.
As stated earlier oxygen is in rare supply within the water as compared to in the air. So fish all fish need a lot of water.
In order to get the desired amount of oxygen and all the other minerals and of course salt. Fish in general have to process all this water.
With this insane amount of water flushing around it comes as no surprise that after taking all the goods out they will still have a silly amount of pee left.
This urine is extremely diluted but still has its uses for example plants yep those plants can still use fish urine to help them grow.
Why Freshwater Fish Don’t Get Thirsty
Freshwater fish reach perfect homeostasis without the need to swallow or ingest water in the same way we do.
Because of this their salt intake is regulated by gills and those Ionocytes cells we spoke about earlier and the rest of the water is taken via membranes all across their skin.
The fish has not had a single drink yet it has not swallowed any water. In fact, there are mechanisms in place to stop water from entering the throat and oesophagus especially while they eat.
And their digestive system has enough to do dealing with uneaten food and food waste in general check out do fish poop how fish poop and why fish poop and of course what is fish poop to learn more about nutrients and how fish work.
Also, the nutrients minerals including salt and potassium are perfectly balanced and so the fish is completely hydrated at all times.
Hence freshwater fish definitely do not get thirsty and they don’t need to drink in order to gain nutrients or indeed to regulate salt or stay hydrated.
Why Freshwater Fish Don’t Swallow Or Drink Water
If freshwater fish were to drink water in a conventional way the same way that we drink water by ingesting.
Swallowing the water and allowing it to be digested in the stomach. Well, this would be highly problematic for the fish as there would be an imbalance of oxygen and salt.
There would be a major shortage of these important elements and if they were able to continually drink water they would blow up like balloons.
Until pop, they explode.
Do Freshwater Fish Drink Water And Do They Get Thirsty Conclusion
In wrapping this post up we can definitely conclude that freshwater fish don’t that’s right they do not drink water.
In fact, if they did it would course more problems than is worth for the poor little tykes. Also, these fish don’t get thirsty as there are no mechanisms in place for this to happen. Indeed it’s the opposite as they absorb the water and treat the water via gills & skin in the process called osmosis.
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