What Can You Put in a Tank with Seahorses?

7 min read

Seahorses are a unique species of fish. They are lovely to keep as pets and watch while swimming. Unfortunately, they are delicate and may not survive in a tank if not well taken care of. They cannot cope with serious competition.


They live better when kept alone in a tank. However, that does not mean they cannot survive with other critters in the same tank as long as you choose their companion wisely, so what can you put in a tank with seahorses?

You can put other slow-moving, non-aggressive critters, plenty of decorations with hitches, live rock, 0.5-1.5 mm aragonite sand, extra filtration, a protein skimmer, and a heater with a heater cover, in a tank with seahorses.

Seahorses are best kept alone or with other seahorses of the same species. If you wish to keep another animal with a seahorse, choose an animal closely related to the seahorse.

However, seahorses can still live peacefully with snails, feather dusters, scooter blennies, hermit crabs, firefish, gorgonians, royal grammas, and pajama cardinals.

The filter or pump needs to have lower settings for slow-moving water, and you should put plenty of hitches for seahorses to hang on to with their tails.

Seahorses are not the easiest pet to set up for and definitely not for beginners, so let’s dive into more detail…

Issues to Consider Before Choosing a Companion for Seahorses

Seahorses have many features that make it challenging to keep them with other aquatic animals. You must consider these features critically before choosing a companion for your seahorse. They include:

  • Slow Movement

The first factor to consider when choosing a tank mate for seahorses is the speed of the other animal. Seahorses are among the slowest swimmers, and they rest most of the time.

If a seahorse is kept with a highly active animal, the animal may outpace the seahorse and deprive it of swimming space and food.

  • Lack of a Stomach

A Seahorse has no stomach. This means it cannot store food. It must feed continuously. However, it is very slow in movement and feeding.

If you keep it in the same tank with another fish or animal that feeds on the same kind of food with seahorses, then it may not be able to compete favourable.

This may lead to starvation. However, it can survive very well with other marine animals like snails that will not compete with it for food.

  • Lack of Defense

In the wild, a seahorse depends on its vision and ability to camouflage for defense. The fish has a pair of eyes that can focus on different places simultaneously. That enables it to spot a predator on time and take action.

However, it is too slow to escape predators by swimming away. It will instead change its color to match its surroundings and blend with its environment.

This isn’t very effective in a small tank. That is why you must not keep a seahorse with a predator.

Luckily, not many aquatic animals prey on seahorses. This is basically because their bodies are covered by bony plates.

  • Lack of Scales

Although seahorses are bony fishes, they do not have scales. Instead of scales, their bodies are covered with bony plates.

The lack of scale exposes them to infection. You must be careful which critter you put in a seahorse tank so that it will not bring disease along. Before bringing a new critter to a seahorse tank, you should first put the critter in quarantine for about a week.

  • Extensive Courtship Behaviour

A male and a female seahorse can engage in a courtship dance for up to three days before they finally mate. Also, the animal is typically monogamous, and the male carries the fertilized egg throughout the gestation period.

However, during this period, the female will be visiting every day to create a good bond with the male. During this period, these two animals are better left alone in the tank.

  • Fragile Babies

Seahorses are among the few animals in which the male carries fertilized eggs till the young ones are born. This is actually to increase the rate of reproduction.

The eggs are produced by the female, and after fertilization, she will transfer them to the male that will carry them throughout the gestation period.

While the male is carrying the eggs, the female is busy producing another round of eggs. Immediately after the male delivered the young ones, he is ready to mate again. Most of the time, the female would also have been ready.

The implication of this is that the young ones are left to fend for themselves. If they are crowded with other species of animals, it may significantly reduce their chances of survival.

  • Strict Water Conditions Required

Seahorses require strict environmental conditions to survive.

Because they swim upward and not sideward, their tank must be tall.

Seahorses have specific water temperatures of 76 – 80 Fahrenheit that can support them based on the specific species.

Their water must be within a strict alkaline level, usually with a pH between 8.0 and 8.3.

The advice that seahorses prefer slow-moving water is outdated and can be dangerous. Seahorses need moderate water movement or approximately 10-25 aquarium volume turnover per hour. This helps filter the water faster since seahorse’s are susceptible to disease.

Seahorses love to rest and require hitching posts for attachment.

Because they are susceptible to infection, the tank water must be adequately filtered constantly.

Any other critters that share a tank with a seahorse must also be able to survive under these conditions.

If the conditions are not strictly adhered to because of the other critters, then the seahorse may be at risk.

Filter/Water Pump

We’ve found that a HOB hang on the back filter or a canister filter (kept separate below the tank) is best for seahorses. This way, the filter is outside the water and provides more space for your seahorses.

Higher Power – Regardless of which filter you choose; you will need a filter with power ratings higher than the size of the tank that you have. Because seahorses don’t have stomachs, they pass a lot of undigested food.

Since filters are designed for fish, the higher power will help filter the extra waste load that seahorses create.

Moderate Water Flow – The advice that seahorses need slow-moving water is outdated so make sure they have moderate water flow or approximately 10-25 aquarium volume turnover per hour.

Protein Skimmer

Slow-moving water can lead to a lack of oxygen in your seahorse tank because water movement is critical to cycling oxygen through a tank.

Sometimes dead zones are created in the tank where water is standing and not being cycled. These dead zones have little to no oxygen!

Also, seahorses need their water extremely clean since they don’t have stomachs to aid with digestion, making them more susceptible to bacteria.

Because seahorses don’t have a stomach, they digest food very fast. In the wild they will eat 30-50 times per day, making more poop, which they are more susceptible to than other fish!

Most seahorse owners install a protein skimmer. A skimmer uses outside air to form bubbles in your seahorse tank.

Waste attaches to the bubbles which then travel to the ‘collection cup’ in the skimmer where the waste is removed. These bubbles bring in more air for oxygen and help remove waste.

Adjustable flow powerhead – Different from a protein skimmer, it can be placed in dead zones to create a gentle current to keep the water moving. This helps bring in outside air to oxygenate the water and ensure all of your water is run through the filter.


The most important decoration to have on your seahorse tank are hitches. This is anything seahorses can wrap their tails around (hitching) to just hang out and relax.

Gargonians and faux corals make great hitches. Anything that is easy for them to wrap around and safe for their tank.

Make sure you buy hitches through your pet store or authorized online dealers. Don’t just grab anything and put it in your tank because it could contaminate your water.

Live Rock

Live rock is great for seahorses because it helps keep the slow-moving water clean. Just make sure you purchase it through authorized dealers to ensure it is properly cured.

Uncured live rock can contaminate your tank.

Aragonite Sand

It is recommended to go with a bare bottom tank for seahorses because of the extra waste and slow-moving water.

You already have a more difficult than average tank to keep clean so sand will just add to the headache.

If you are dying to put sand in your tank for appearance, then you should put 0.5-1.5 mm aragonite sand.

The finer sand keeps waste from sinking in and becoming embedded.

Make sure you have adequate water flow along your sand bed to keep waste from building up. This can be achieved with a powerhead mentioned above.


You can put any basic aquarium heater in your seahorse tank, just make sure it is covered so your seahorse doesn’t burn their tail.

Seahorses like to wrap their tails around anything, and a heater can be the perfect shape if it isn’t covered.


A seahorse is very inactive; hence is best kept alone or with other seahorses.

However, it can also be kept safely with other animals that are equally inactive or pose no form of danger or competition to the horse.

When choosing a tank mate for seahorses, you must consider the activity level of the tank mate, how the tank mate is going to compete with the seahorse for the available food and swimming space, and whether the other animal will be able to cope with the tank condition that is favorable for seahorses.

Another important factor is the susceptibility of seahorses to infection. Hence measures must be taken to ensure any new animal introduced into a seahorse tank does not come with a risk of infecting the fish.

Also, make sure you have the proper equipment as described above.

Seahorses are delicate and not for beginners so follow the tested and successful guidelines we have outlined above!

Written by:

Pet Aquariums

Have you any questions?