Are Emerald Crabs Safe For Seahorse Aquariums?

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Crabs are crucial members of aquarium clean-up crews as they are great at scavenging and making sure all waste is consumed. The emerald crab is a firm favorite when it comes to crew members, but are these crustaceans safe for seahorse aquariums?

Emerald crabs are considered safe for seahorses and they can be kept together successfully. Provided you meet the necessary conditions and proceed with caution you should be fine. However, there are a few outliers who will display behavior that might not be ideal for sensitive fish like the seahorse. After all these crustaceans are opportunistic given the situation they are willing to prey on anything to satisfy their hunger.

Emerald crabs are one of the best members to add to a clean-up crew. These crabs are very beneficial and are almost suitable for just about any tank.

They are generally peaceful and are considered to be safe for seahorse aquariums.

But just like other crustaceans although they are quite small they do have a mean streak and it can show up every now and again if the situation arises.

This is why they are regarded as semi-aggressive since they can display unwanted behavior depending on their environmental conditions.

However, if kept and maintained properly these crabs make great additions to a seahorse aquarium.

Just remember to always proceed with caution since there is always that chance of uncertainty hence possible aggression.

Conditions For Keeping Emerald Crabs.

When keeping emerald crabs with seahorses there are a few conditions that need to be met. This is required in order to provide the best environment for all inhabitants to co-exist peacefully.

1. Even though all emerald crabs have the tendency to be aggressive, females tend to be less aggressive and more composed. The males are often problematic when conditions aren’t met.

Therefore always choose female emerald crabs to increase your chances of compatibility within a seahorse-specific aquarium.

2. Emerald crabs are quite small around 2 inches in length yet they are voracious feeders. These bad guys have really large appetites that must be satisfied daily to keep them from scouting on other tankmates.

Normally they will mind their own business scavenging on leftover meat and algae.

But if resources are scarce and they aren’t being fed properly it will trigger their aggressive nature forcing them to look at other tankmates as possible prey.

To prevent this feeding frenzy always make sure your crew members are satisfied to keep the system running peaceably.

3. From what I’ve heard there are two types of crabs that resemble emerald crabs. One has flat tip claws and the other has pointed tip claws.

The flat-tip ones are herbivores in general but can scavenge on meat if needs be. These are regarded as true emerald crabs.

The pointed-tip ones are carnivores and these guys are known for preying on other small tankmates when they aren’t satisfied.

For this reason, make sure you speak to your Local pet store or breeder and get the right emerald crab.

Don’t let anyone fool you into buying lookalikes, it’s imperative that you choose the right species that are compatible with seahorses.

4. Emerald crabs do best in larger tanks with enough surface area for them to explore.

A small tank will keep them limited and restrained which can result in all sorts of unwanted behaviors.

A good-sized spacious tank will provide enough room for them to gather resources keeping them satisfied in the process.

5. Keeping more than one emerald crab is not often recommended since there is a possibility for aggression towards each other.

Having one crab is sufficient but if you intend on keeping more than one make sure you have at least 20 gallons per crab.

This will make sure all occupants have their own territory and the chances of aggression are minimized.

6. When keeping emerald crabs it’s advised to not keep snails since they are easy targets for them to prey on.

Snails are slow-moving creatures that are bottom dwellers and may cross paths with the emeralds and they can be devoured in no time.

For the best possible outcome, keep snails away from tanks that emerald crabs are sheltered in.

7. When algae and leftovers are scarce in an aquarium make sure you are providing supplemental food.

This is a crucial part of making them remain at peace in a community tank, if not their opportunistic tendencies will have them preying on livestock.

You can feed them dried nori, chopped shrimp, etc. This will help keep them satisfied preventing them from being problematic.

8. Emerald crabs love to hide so create plenty of hiding spots with live rock and reef work so they can have a place of refuge.

This will also prevent them from causing disputes within a tank since they can easily take cover whenever they feel threatened.

Benefits Of Keeping Emerald Crabs.

1. Emerald crabs are one of the best at dealing with nuisance algae which is a problem for many hobbyists.

Under the right conditions, these guys make great additions to a seahorse aquarium. They will keep algae controlled reducing the maintenance that’s regularly required.

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

Over time this waste breaks down causing all sorts of imbalances in the chemistry of the water.

By adding these crabs they will consume all leftover food before it can even start to break down.

3. Due to the great maintenance ability of these crustaceans they overall help maintain good water quality.

Seahorses are very sensitive to water quality and even the slightest changes can greatly impact their health in a negative manner.

Yet again the added benefit of this crab will assist in making sure water quality remains stable and suitable enough for all tankmates to thrive.

4. Their distinct color adds diversity to a somewhat sedentary seahorse aquarium. Normally seahorse keepers keep their ponies in species-specific aquariums.

These aquariums are sometimes boring, dull, and not aesthetically pleasing. But just adding a few tankmates like these brightly colored crabs, will add pops of color and activity to your tank.

5. These guys play an important role in aquarium husbandry. They assist in clean-ups whether it’s sifting through the sand, cleaning up rock, or scraping up debris.

Every effort of theirs is seen and admired at least for aquarium enthusiasts who know the struggles of maintaining an aquarium.

Potential Risks.

Even though emerald crabs are a great choice for saltwater aquariums they are sought out by many for their great scavenging ability.

But they are crustaceans and are opportunistic.

While they are regarded as safe for seahorses it’s just those rare exceptions and uncommonly abrupt individuals you must be wary of.

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.

That’s the reason there are conditions that must be met when keeping them. So be mindful of these potential problems.

2. They may be entirely peaceful and inoffensive when they are small, but even a small crab can cause a lot of trouble as it grows.

They have the ability to go from docile to predatory really quickly if the environment they are in doesn’t fulfill their current demands.

3. Seahorses aren’t really a direct target for these crabs since the larger seahorse species get really big.

Also, seahorses normally remain within the water and not really at the bottom. But their tails are at risk of being attacked, in worst-case scenarios.

Always be mindful and observant so you can act accordingly since even the slightest bruise or injury on a seahorse can prove to be fatal.

4. Emerald crabs should never be paired with dwarf seahorses(Hippocampus zosterae). These are very small species that will be seen as prey for the crabs.

If paired together they will be consumed in no time. It’s better to keep these crabs with the bigger species like H. Erectus etc.

5. Keeping emerald crabs with seahorses under unfavorable conditions can bring about competition for resources and the seahorse can be outperformed very easily.

This just shows the importance of having sufficient food to make sure all tank inhabitants are kept satisfied and thriving.

I would suggest you target feed your seahorses rather than placing food at a food station. This will make sure that these slow eaters obtain their daily nutritional requirements.

6. Emerald crabs are scavengers and most importantly algae busters. This can pose a possible problem since algae attaches to the bodies of seahorses and over time this builds up.

This can be seen as a potential food source for these crabs and they can groom them which can be too much for seahorses to handle.

This can lead to stress leaving the seahorse in a compromised state.

Obsessive grooming and bullying is a potential risk, although it’s uncommon.

7. Emerald crabs are regarded as reef-safe but can predate on coral if hungry. This puts added risk on the health of corals in your aquarium should you choose to add them to your tank.

Even though it’s not common for them to eat coral, they will attempt to consume at least the dead parts of it if unsatisfied.

Final Thoughts

So to sum it up, “Emerald crabs are safe for seahorse aquariums 9/10 times but there is still that 1 percent that will present with unwanted behavior,” said ocean rider at

These crabs come with great benefits and will make for good tankmates if certain conditions are met.

Overall I feel that everything comes with risk, even emerald crabs. It’s not a shocker, just create a suitable environment for them to thrive and you should be fine.

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