Why Saltwater Fish Drink Water It’s A Thirsty Job

In a previous post, I explained how I was sitting and wondering why my fish tank’s water levels remained pretty stable.

Even though there must be some slight evaporation happening check this wonderful post about my fish tank’s water keeps evaporating.

And the fish must be peeing and that we have twenty-odd fish in our tank. So what gives? Well, we came to the conclusion freshwater fish absorb water via their gills and through their skin. 

So they take a lot of water in but pee it back out so to speak check my awesome post on freshwater fish and why freshwater fish don’t get thirsty.

 Also, we verified that they indeed do not drink water in fact it’s dangerous for them to do so.

What About Saltwater Fish?

Do they Drink Water?

Yes, saltwater fish drink water as their bodies contain less salt than the water they reside in hence they need to drink the water & pee the excess salt out in order to stay hydrated.

Why Saltwater Fish Need To Drink Water In More Detail

Let’s take a deeper look at the processes and why saltwater fish differ from their cousins the freshwater fish.

Saltwater fish lose copious amounts of water yes that’s my way of saying they lose a lot of water. They lose this water in two ways.

Firstly they lose water via their gills because the water is so salty these little salt fish need desperately to keep this salt out.

Put it this way our saltwater fish is dealing with water that has three and a half times more salt than our freshwater friends.

The second way that they lose water is via their skin yes saltwater fish are designed in the opposite way to freshwater fish.

Freshwater can take water in via osmosis through skin membranes but saltwater because of the high salt content lose water via osmosis through skin membranes.

 Dehydration And The Need For Even More Water

Now our buddy old salty has lost a serious amount of water partly because his gills are desperately keeping salt out.

As well as losing water via the gills they lose via osmosis through skin tissue. Now the dehydration is about to kick in what can be done?

Amazingly our mate old salty is going to drink that’s correct you heard right they allow themselves a good old drink of water.

But how’s this helping them now they’ve drunk a load of salt with that water? What was the point if they’re gonna get even more dehydrated.

Kidneys Pump Salt Into Urine

Saltwater fish have a unique answer to this problem too. These crazy heroes have remarkable kidneys.

Yep, these kidneys can pump out copious amounts of salt that’s right loads of salt can be pumped out and pushed into the fish’s urine.

So the fish just pees a lot yep a very salt-heavy pee.

Constant loss of water For Saltwater Fish

What we have to consider is this huge loss of water that saltwater fish have going on. What was to happen if they lose too much water?.

Well believe it or not the exact opposite would occur as that of the freshwater fish what’s that you ask.

The freshwater fish will expand from lack of salt as it’s constantly pumping as much salt in as it can. If the salt wasn’t there or not enough then that fish will blow up like a balloon and explode.

In the case of our saltwater friend well the opposite is true. they would become so dehydrated they would shrivel up and die.

Well, they would properly die long before from heart problems.

Shrivel Up Or Organ Failure

An interesting hypothesis is another big word for today. I need to stay in my lane and keep things simple think.

Anyway, before a saltwater fish shrivelled up and died because of too much salt. The poor thing would have already died of repository failure heart attack and or other organ failures.

As not enough water would be being pumped into the blood. The blood would become thicker and thicker full of salt and this would make it so hard for the fish to pump that thick salty blood around its body.

Saltwater Fish Drink Water

Do Saltwater Fish Get Thirsty?

Now the vast majority would say something along the lines of thirst being a conscious thing that you have to now your drinking.

Or they are not instinctively or actively seeking out water in order to drink. And that it’s a reflex action and they have no idea that they are drinking.

These are interesting points but I beg to disagree with them as they are condescending, to say the least.

These fish have been beautifully designed in a way to survive with mechanisms in place to combat and balance nutrients minerals as well as water intake.

Look at how the gills are perfectly balanced to secrete salt and the kidneys even the urinal tract not to mention the fact that saltwater fish are even capable of drinking in the first place.

As we know freshwater fish have been designed not to drink. All that to say this how do we as humans know were feeling a tad dehydrated?

Obviously, the saltwater fish are able to determine that they are in need of water and they drink the water ie they do get thirsty.

Indeed yes some fish get thirsty saltwater fish get thirsty.

In Conclusion, Yes Saltwater Fish Do Drink

Water And It’s A Thirsty Job

In conclusion, I’d like to sum things up by saying saltwater fish need to drink water in order to keep the balance between salt and water exact.

Even though they are very efficient at flushing salt back out via their gills and via osmosis through the skin, it’s perfectly clear this is not enough.

These fish need to do more work in order to get the correct balance and they need to get rid of more and more salt in order to function.

This is indeed accomplished by drinking a tone of water and allowing the kidneys and urinal track to expel the unwanted salt.

Let us finish by saying it’s thirsty work being a saltwater fish.