Can Hermit Crabs Be Kept With Seahorses? Full Compatibility Guide.

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Crabs are an excellent feature for seahorse aquariums since they are very beneficial and exciting. However, adding them to a seahorse aquarium is very debatable. Some say they aren’t compatible while others are already successfully keeping them. So what’s the verdict?

Hermit crabs can be kept with seahorses under the right conditions allowing them to co-exist peacefully. While not all hermit crabs are compatible with seahorses there are a few that fit the criteria of becoming potential tankmates. However, you must proceed with caution since crabs are opportunistic scavengers and even the most docile species could potentially display aggressiveness.

Hermit crabs are a type of decapod crustacean belonging to the superfamily Paguroidea. Though they are called crabs, they are actually more closely related to lobsters than true crabs.

These crabs come in a variety of different types but there are only a few types who are famous clean-up crew members for most saltwater aquariums.

They come in an array of temperaments while some are peaceful others are aggressive although all can display aggression depending on the circumstances.

With regards to seahorses, only a few types of hermit crabs are compatible and are probably safer to keep compared to others.

These are the micro hermits/ dwarf hermits that grow to about an inch or two when matured.

These smaller hermits are more suitable for seahorses due to their smaller sizes and the fact that some seahorses grow pretty big so they won’t be seen as prey.

Provided you keep dwarf seahorses away from hermits you should be fine since dwarfs are easy targets for these scavengers to prey on.

However, there are some cases whereby seahorses were the attackers preying on small hermits.

According to some forums that I’ve seen, there are actual real-life cases where bigger seahorses like H.erectus and H. reidi butchered these hermits removing their shells and consuming tiny pieces of their bodies.

This is a potential risk that you need to look out for if you do decide on keeping hermits with seahorses.

After all, there could be attacks from both sides, seahorses, and hermits. One can never be too certain when it comes to these things, always proceed with caution.

Conditions For Keeping Hermits With Seahorses.

Even though hermit crabs can be kept with seahorses there are a few conditions that must be met in order to have the best chances of success.

You see crabs will be crabs regardless of what species you choose even the most docile ones have the ability to display aggression.

Your only option in keeping all tankmates safe is by following strict rules and making sure these conditions are adhered to.

1. Hermit crabs require sufficient space for them to explore. Even though they are small they are naturally wired to scavenge upon whatever they may find.

These guys aren’t lazy and are willing to go to extreme lengths to sustain themselves. Make sure the tanks you choose are big enough, like these ones for them to roam freely

You also need to provide a suitable substrate bottom, these janitors like to burrow in the sand and may only come out at night.

An inch or two of soft aquarium sand should be ideal to house these crustaceans.

2. Only suitable hermit species are allowed to inhabit seahorse aquariums. Among the many species micro hermit crabs are the best fit for seahorses.

These ones are the safest and give the best chances of co-existence.

3. You should not pair hermit crabs, especially micro hermits with other more dangerous tankmates. Keep them away from predatory fish, aggressive invertebrates, and big marine life which can prey on them.

Choose your tankmates carefully making sure that all inhabitants can live in harmony.

These micro hermits should also be protected not only seahorses.

4. Keep hermits away from dwarf seahorses since they are too small and unsuitable as tankmates. Rather go for the bigger tropical species Like H.erectus, H.reidi, H kuda and H comes.

These seahorses are more size appropriate for hermits and won’t fall prey.

5. Even though the bigger seahorse species are the best choices, choose the younger ones who aren’t very big.

From what we’ve seen mature seahorses can prey on micro hermits, so for the safest environment for all tankmates go for the younger seahorses who are still developing.

This allows for all tankmates to grow together evening the playing field.

6. Do not overstock these invertebrates, a general rule of thumb which I feel is right is two hermit crabs per 10 gallons of space.

So if you setting up a beginner seahorse aquarium which should be at least 30 gallons you can stock 6 hermits comfortably.

I know other aquarists keep more but for the best chances of providing a peaceful tank stick to lower densities of tankmates giving all inhabitants their own space.

7. Hermit crabs are nocturnal and will be most active at night. Even though they hide inside their shells they do require alternative hiding spots to seek refuge.

This is important for them since it makes it possible for them to remain safe when threatened or stressed.

You can put together rock, plants, and other reef structures to create nice crevices and holes for them to hide.

8. Hermits are omnivorous scavengers and will eat both plants and meat. But there may be certain times when food might be scarce.

In these situations, you must provide supplemental food like shrimp, mysis, or even pellets. This will help sustain these crabs if not they will predate on other smaller vulnerable tankmates.

9. Micro hermits combined with an assortment of seahorse-safe snails are all you need for a good clean-up crew. Avoid other possible choices since they may not be suitable for micro hermits.

10. Make sure you provide a constant supply of empty shells for hermits to inhabit as they molt. These crabs are very fragile and vulnerable without their shells.

As they grow they will need bigger shells to house them, be sure to provide this as it is essential to their well-being.

11. As with all invertebrates they do not tolerate copper-based medications be sure to stay away from these ingredients.

Safest Hermit Crabs For Seahorses.

1. Scarlet Reef hermit crabs (Paguristes cadenati)

Scarlet reef hermit crabs are one of the most popular reef janitors who are sought out by many hobbyists and enthusiasts in the field.

These crabs although small (1-2 inches), are voracious eaters feeding on detritus, algae, and leftover meat.

They help in assisting with nuisance algae which is a problem for most aquariums.

They will also do well cleaning up after seahorses who are poor eaters.

The fact that these crabs are hardy, easy to care for, peaceful, and beneficial, are all great attributes that make them ideal janitors for seahorse aquariums.

2. Dwarf Blue-leg Hermit (Clibanarius tricolor)

The dwarf blue-legged hermit crab is another good candidate for seahorses and will greatly benefit their aquarium without the added risk.

These blue/red colored crabs may be smaller in size reaching around 1 inch but they are great omnivores with voracious appetites.

These guys take cleaning to the next level when it comes to fitting into the tiniest of spaces to access resources.

Blue hermits will help with algae, debris, and leftover mysis which is often a problem in a species-specific aquarium.

They also aerate sand substrate encouraging the growth and activity of beneficial bacterial.

But be sure to provide supplemental food since these guys will prey on other vulnerable specimens when they are desperate for resources.

Overall, they are peaceful, colorful, and easy to care for making them great additions to a seahorse aquarium.

3. Left-handed/Dwarf Zebra Hermits (Calcinus laevimanus)

Left-handed hermit crabs are a very peaceful, social, and interesting species that are suitable for sedentary tanks like the seahorse aquarium.

They have quite an interesting appearance with colored pinchers as well as white and orange bands that wrap around their dark legs.

These guys have distinctive features that are easily recognizable such as their large oversized left claw that is often used for defense.

These guys are herbivores scavenging on detritus and nuisance algae but they do need supplemental food in the case of insufficient algae.

Dried seaweed is a great supplemental food and they will do well nibbling on it throughout the day.

Overall these guys are peaceful, easy to care for, and great for controlling algae. These hermits are yet another good addition to a seahorse aquarium.

4. Mexican Red Leg Hermits (Clibanarius digueti)

The red-legged hermit crab is a tiny yet powerful addition to an aquarium as they are extensively used in marine aquariums to combat nuisance algae.

These crabs often reside on rocks or hidden in the substrate and will clean up everything that’s within their reach.

They grow to about 1-2 inches and are considered reef-safe, however they may feed on macroalgae should you choose to keep them.

They will also need supplemental food like dried seaweed and pieces of shrimp if algae is scarce.

The only issue with these crabs is that they must be provided with enough shells for them to inhabit or else they will attack their other counterparts or snails and steal their shells.

Overall they are easy to care for, peaceful (with exceptions), and compatible to co-exist with seahorses.

Benefits Of Keeping Hermit Crabs.

These tiny powerhouses add a lot of benefits to any tank they are sheltered in, these benefits include

1. They help get rid of debris and detritus build-up which is a fear when keeping seahorses since it leads to the decline of water quality.

Adding these crustaceans will help assist in keeping waste at its minimum preserving the life of the aquarium inhabitants.

2. Herbivorous hermits help with nuisance algae which can be problematic in a saltwater aquarium. But due to the voracious appetites that these small creatures have they help control these pests.

Depending on how many individuals you add, they all will play a role in assisting the aquarium to keep algae growth to a minimum.

3. Overfeeding is also a problem when it comes to seahorse aquariums since these ponies are passive feeders lots of food goes to waste.

Many hobbyists often choose to target feed which helps keep waste down but due to their messy tendencies and heavy bioload, they need assistance.

Seahorses are either releasing waste through their rear end or expelling food through their vacuum snouts with each mysis they suck up.

Over time this waste breaks down causing all sorts of imbalances in the chemistry of the water. By adding these crabs they will consume most of the leftover food before it can even start to break down.

This helps prevent the release of harmful chemicals such as ammonia and nitrite which is a toxic substance to marine life.

4. Hermit crabs come in an array of colors and distinctive features perfect for adding pops of colors to an aquarium.

They also add diversity and activity making the tank more aesthetically pleasing.

5. Dwarf hermit crabs are easy to care for and are perfect for beginners. Once you have the right setup, access shells, and ample food they will do well.

6. They are great janitors making sure all algae is consumed, leftover mysis is slaughtered and debris is all taken care of.

Thill will reduce the maintenance required allowing for less frequent husbandry.

Potential Risks.

Like with any other species of crab, there are always risks that you’d incur if you decide to keep them, after all, there are no crabs that are completely safe.

While some may be peaceable and docile when young they often grow to become great opportunists taking advantage of every situation to make sure they survive.

However, hermit crabs come small and remain small, reducing the risks that are normally associated with keeping crabs.

These are the potential risks you should expect when keeping arrow crabs with seahorses.

1. There is always a chance of aggressive behavior. Although uncommon it’s a risk that comes when keeping crustaceans.

At the outset, you must know that these guys are opportunistic and they will take every opportunity given to them.

If any marine life is small enough to fit in their mouths chances are that they will try to consume them in desperate situations.

2. Be careful with the bigger mature seahorses who can prey on these micro hermits and can easily consume them.

Even though it’s a very rare occurrence it’s still a possibility.

3. Even though hermits won’t harm seahorses directly since they are bigger than them there are a few cases of hermits attacking seahorses while they are at rest.

When at rest, their prehensile tails are wrapped around hitching posts leaving them in a compromised state.

Look out for these attacks and observe your seahorse’s tail regularly to check for signs of bruising or injury since even the slightest injury can be fatal.

4. Since hermit crabs inhabit shells to house them they need a constant supply of shells as they grow and molt.

If not provided they will attack other tankmates like snails, and other crabs to steal their shells since without an appropriately sized shell these crabs are left defenseless and vulnerable.

Watch out for this or you can just avoid this by providing enough shells of different sizes for them to choose from.

5. They can eat fleshy macroalgae and may totally consume them if hungry. Should you keep macroalgae in your aquarium, keep this in mind.

6. While hermit crabs are reef safe there are some who will nibble on corals if the need arises.

This isn’t the case with all hermits but depending on the type of hermit you choose for your aquarium, just be mindful of these potential risks.

Final Thoughts.

Hermit crabs are a great feature for a saltwater seahorse aquarium and they can co-exist peacefully under the right conditions.

Should you decide to add them to your seahorses aquarium make sure you meet the conditions needed for the best chances of success.

Nine out of ten times they will do well with seahorses it’s just that uncommon outliers that you might face every now and again.

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