How Big Are Seahorses? [Explained]

How big are seahorses? Normally, seahorses can be as big as 35cm in height and 0.4-1 lbs in weigh. Seahorses can vary in size depending on their type. But the biggest seahorses are usually the Australian Bigbellied seahorses. Although most of them grow up to 18-28cm in height, some excel in size.

You can come across seahorses across the earth in different environments. That’s right, they can be in temperate waters or tropical waters. And these majestic beasts seem to be quite interesting to study.

In this article, you’ll find all you need to know about how big seahorses are. That’s not all. We’ll also talk about some intriguing knowledge about the tiny horses from underwater. So let’s dive into it without further ado.

How Big Are Seahorses?

If you’ve ever wondered how big seahorses can get, you’re in for a treat. You might be able to keep the smaller species as pets. But the biggest ones will actually amaze you.

Let’s start with something small at first.

A species of seahorse called the ‘Hippocampus denise’ is quite possibly the smallest. They can have a length of around 16 millimeters. That’s right. It’s even smaller than some of your fingernails.

So, by now, you probably have an idea about how the size varies depending on the species. That’s pretty much the point of this article. But if you must know, we’re here for you.

The big-belly seahorses, aka the pot-bellied ones, can measure up to 35 centimeters. They are scientifically known as ‘Hippocampus abdominalis.’ You’ve heard of foot-long sandwiches; well, this is a foot-long seahorse.

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But this isn’t the average length, of course. Most of the seahorses are around the 18-28cm range. But this still makes them the biggest seahorses in the world.

length of a seahorse
Length mesurement of a Seahorse (Source:

How Much Does a Seahorse Weigh?

If you’re curious about how big they can get, you might also want to know how much they weigh. Well, there’s no catch. There are about 47 different species of seahorses. And they definitely vary in weight.

Seahorses also vary in weight when they are in different reproductive stages. But to give you a rough estimate, they usually weigh 0.4-1 lbs. This isn’t a standard, though.

They do gain weight when they get pregnant, though. The male seahorses keep the eggs in the pouch. These eggs remain in the pouch till they hatch. Male seahorses can carry up to 2,000 babies at a time in their pouch.

How Do Big Seahorses Look?

Although different species of seahorses have different characteristics, they have things in common. You might say that they’re often a combination of different animals. Big-bellied male seahorses have something called a brood pouch.

If you think you can feel the scales of seahorses like those of fishes, well, you’re wrong. Their exoskeleton is covered with a fleshy outer layer.

Depending on the species, the crown on top of their head differs. But their crown is usually called ‘coronet.’ This crown encompasses a set of spies. Just like some fishes, they use pectoral fins for steering and stability.

But the sad fact about the bigger seahorses is that they aren’t swift swimmers. So they have to rely heavily on the dorsal fins.

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Here’s a fun fact. Did you know that seahorses can move their eyes independently? That’s right. They can use their eyes to monitor the surroundings without giving away their whereabouts.

how big are seahorses

Are Big Seahorses Fish?

Well, the short answer is yes. These horses from the sea don’t resemble many aquatic fishes. And their lack of scales might give it away. But whether you want to believe it or not, they are ‘fish.’

Although they lack some characteristics of fish, they still have the bladder to swim. And just like fish, they use their lungs for breathing underwater. Since they have a bony structure, most fishes steer clear of them.

But they might get gobbled up by some crabs with pincers. Now that’s a bummer.

Seahorse Diet to Get Bigger

So, what would make the big seahorses continue getting bigger? A good diet, of course! You might not know this, but they lack teeth. And their entire digestive system is sort of different. So what do these horses feed on? You might think they eat plants underwater, right?

Close, but that’s not quite it.

Seahorses actually consume planktonic copepods. Along with these, they also feed on tiny fishes. They actually look pretty funny while having a meal. If you must know, yes, they use the trumpet-like mouth to suck in their prey.

Small crustaceans are no match for the force they pull with. And their metabolism helps them digest all these pretty well.

The biggest seahorses may even consume up to three thousand crustaceans in a day. So you can probably imagine how big they can get.

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Do seahorses have teeth?

No, sea horses have no teeth. In fact, they don’t even have a stomach. We’ve talked about their metabolism in the digestive system already. The food they consume passes quickly through the entire digestive system. That’s why they can consume more in a single day.

Do seahorses have a lot of predators?

No, seahorses don’t have many predators. But they steer clear of giant crabs and crustaceans. If they can get their pincers on seahorses, they’re done for. But most fish avoid seahorses due to the bony structure.

Are big seahorses bad swimmers?

Well, kind of. Whether big or small, seahorses aren’t good swimmers. Their body shape prevents them from swimming adeptly. In fact, if they are caught in a storm at sea, they could even die due to tiredness.


So, I think you got your answer to “How big are seahorses?” in this article. These little creatures can be pretty fascinating when you actually delve into some research. Their lifestyle and food habits play a role in determining how much they’ll grow. But the biggest of the bunch, the big-bellied ones from Australia, can grow up to 11.8 inches or more.

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