When stocking a 100 gallon saltwater aquarium, emerald crabs are a great choice to help keep algae under control. But how many should you add? Here are some quick answers:
Quick Answers
- 5-10 emerald crabs for a 100 gallon tank is a good starting point
- Stock conservatively at first, then add more over time as needed
- Provide plenty of hiding spaces and supplementation to support the crabs
- Watch for aggression, overstocking can lead to crab loss
The specific number of emerald crabs for your tank depends on a variety of factors. In this article, we’ll go over tank size considerations, stocking recommendations, crab behavior, diet and supplementation, tank setup, and more to help you determine the ideal emerald crab population for your 100 gallon aquarium.
Tank Size Considerations
When it comes to stocking any aquarium, larger is always better. Bigger tanks provide more ample room for fish and invertebrates to spread out, which helps reduce aggression and competition.
A standard 100 gallon tank measures 48 x 18 x 24 inches (length x width x height). This provides approximately 75-80 inches of horizontal swimming space (length + width).
As a general rule of thumb, it’s best to allow at least 10-20 gallons of water per emerald crab. This means a 100 gallon tank could comfortably house 5-10 emerald crabs.
However, the aquascape and number of hiding spaces also impact the carrying capacity. The more crevices and rocks and overhangs, the more crabs the tank can support.
Stocking Recommendations
When it comes to stocking emerald crabs, start conservatively and slowly increase over time. Here are some general recommendations for a 100 gallon tank:
- Begin with 5-7 crabs
- Wait 4-6 weeks, then add 1-2 more if algae growth necessitates
- Max out at around 10 crabs, depending on tank conditions
This gradual stocking allows the crabs to establish territories and hierarchies peacefully. It also gives you time to monitor crab health, behavior, and algae growth before determining if more crabs are needed.
Crab Behavior
In addition to tank size, emerald crab behavior also influences ideal population density.
Emerald crabs are highly territorial and will fight with each other for prime spots with the most algae growth. They will also become aggressive while competing for food.
Having too many crabs crowded into a small space increases the chances of mortality from fighting. Stronger crabs may kill weaker ones or rip off their limbs.
Ideally, the tank should have enough terrain and hiding spots to allow each crab its own home range and territory. This prevents constant conflict and competition.
Closely observe crab interactions, especially at feeding times. Ongoing aggression, hiding, or missing limbs are signs the population needs thinning.
Molting Considerations
Another factor to consider is the crabs’ molting cycle. All crabs regularly shed their exoskeletons as they grow. Emerald crabs will hide for several days while in a vulnerable, soft-shelled state after molting.
If shelter space is limited, competition for the optimal molting sites may trigger aggression. Having excess room allows multiple crabs to find secluded molting spots safely.
For these reasons, it’s always better to air on the low side when stocking emerald crabs rather than overcrowd the tank.
Diet and Supplementation
In addition to algae, emerald crabs will scavenge for meaty foods and eat aquarium flake foods, shrimp pellets, and frozen preparations. Providing a varied diet is key to keeping crabs well-nourished.
Supplementing food sources helps prevent excessive algae grazing and competition. Target feed crabs after lights out, as they are nocturnal. Spread food across the tank to allow eating access for all crabs.
Calcium and iodine are vital for proper exoskeleton formation pre- and post-molt. Offer calcium-rich snacks like shellfish and kelp several times per week. This provides trace minerals and reduces algae grazing pressure.
Underfed, malnourished crabs will become more aggressive towards tankmates. Adequate food availability for the stocked population is crucial.
Tank Setup and Design
The aquascape design greatly impacts the number of emerald crabs the tank can support.
Create an environment with ample algae grazing surfaces as well as hiding places. Rock piles, caves, driftwood, and plants provide shelter. Crabs will fight less if each has its own home.
Leave plenty of open horizontal rocks, decor, and tank walls for algae growth. Vertical surfaces are also appreciated.
Since emerald crabs are climbers, a tank lid or cling-resistant surfaces are a must. Provide 3-4+ inches of substrate for burrowing and molting.
Lastly, consider the other tank inhabitants when planning emerald crab numbers. Avoid housing tiny, delicate species that could get pinched. Slow moving fish may become prey.
Other Tankmates
Some good tankmates for emerald crabs include:
- Snails like turbo snails, trochus snails, nerites
- Shrimp like skunk cleaner shrimp, peppermint shrimp
- Many saltwater fish species
Avoid housing emerald crabs with:
- Small goby species
- Seahorses
- Pipefish
- Ornamental shrimp
For a 100 gallon tank, stick to fish that won’t nip at crab legs or be considered food. Medium to large species over 3 inches are best.
Signs of Overcrowding
Be vigilant for any signs of emerald crab overcrowding. Issues to watch for include:
- Excess algae growth on surfaces
- Nipped fins or claws on crabs
- Missing limbs
- Dead crabs
- Crab declanning or falling from surfaces
- Remaining hidden most of the time
- Frequent aggression or fighting
If you notice any of these warning signs, reduce the crab population by rehoming excess individuals. This will re-establish a harmonious hierarchy.
Avoid adding any new crabs for several weeks after removing individuals. This allows the remaining crabs to settle territorial disputes non-violently.
Conclusion
When stocking emerald crabs in a 100 gallon tank, moderation is key. Start with 5-7 individuals, supplement their diet, and provide ample algae grazing room and shelter.
Slowly add 1-2 more crabs at a time if algae is not under control after a few weeks. Max out at around 10 crabs depending on aquascape design.
Overcrowding crabs leads to aggression, competition, and deaths. Monitor crab behavior closely and watch for signs of excess such as hiding, injured appendages, or excessive algae growth.
With the right population density, tank size, shelters, and diet, emerald crabs make excellent crew members in a saltwater aquarium. Their algae grazing helps keep nuisance algae at bay.
