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Many aquarium owners that love keeping inverts think of shrimp before crabs, probably because the former is more readily available. However, if you allow yourself to experience the thrill of keeping crabby-critters, you will surely enjoy the hobby so much more.
The only challenge of having crabs is that they are pretty unexplored, meaning there is limited information out there. Moreover, unlike shrimp that are fully aquatic, your critters will require an area of land in the tank to regularly emerge from the water.
In general, there are not many fully aquatic freshwater aquarium crabs, but putting a branch, rock, or wood that comes above the waterline will solve most challenges associated with keeping your crabbies in a fully submerged environment.
Just make sure that your aquarium has a cover and the branch is nowhere near the edge for obvious reasons; escape.
That said, the only almost fully aquatic crab I think would live in your tank without much need for a dry area, is either the Pom Pom or Thai micro crabs, everything else in between will need to venture outside for a quick bask.
Read on for more insight on keeping freshwater aquarium crabs, plus which species are most likely to survive fully submerged.
Do Freshwater Aquarium Crabs Need Air
Crabby aquarium critters are amazing creatures with a rather bizarre ability to breathe both in aquatic and terrestrial environments.
Of course, like any living thing, freshwater crabs need air. But they do not need to be always out of the water to breathe, which is also part of the reason most species lead a semi-aquatic life.
In case you are wondering why then is it necessary to have a half-water half-land aquarium when keeping crabs, probably the most logical and least complicated answer is…
…it’s just how they’re wired.
For starters, just because crabs can breathe in water does not mean it is an elaborate failproof system, but rather a half and half kind of operation. The critters will be submerged for a while but need to come out the next minute for air.
Some species like fiddlers crabs require air and more time on land than others like Pom Pom crabs.
Crabs also prefer things on the warmers side, both in the water and on-land. The little piece of dry area in the aquariums allows them to have some time to bask and take in the much-needed warmth.
Ideally, allow two parts water to one part land, though this can vary by species. Use rocks, sand, and other aquarium safe hardscapes to build the dry area in your aquarium.
The habitat can also be established underwater using a one-gallon glass pickle jar, an extra aquarium air pump, and an airstone, and some rocks or sand.See the steps here.
Fully Aquatic Crabs For Your Freshwater Aquarium
As I mentioned before, there are not many species of fully aquatic freshwater crabs, especially not in the local fish stores.
Even so, with a little hard work and some element of luck, you might get types like the Pom Pom or Thai micro (false spider) crabs that’ll live entirely in the water.
Below are the few fully aquatic crabby-critters you are most likely to find in local fish stores.
#1&mdashPom Pom Crabs
The Pom Pom aquarium crab is a very engaging, entertaining, and durable candidate for a freshwater community aquarium.
Unlike most freshwater crabby-critters, this species is truly, fully aquatic. Albeit, keeping your water line relatively low (or adding a lid to your aquarium) is recommended as they are seasoned escape artists.
Pom Pom crabs are reportedly present throughout many tropical and sub-tropical regions in Africa, Asia, and Australia. As such, it’s advisable that you only add them in fully-tropical tanks, with parameters akin to those the crabs' experience in the wild.
Your aquarium will also need to be well filtered and continuously maintained in pristine conditions. You especially don’t want chlorine or copper traces from municipal water sources and fish medication in your fish tank.
A little salt won’t harm your Pom pom crabs. Actually, they seem to enjoy brackish water, and they’re only deemed to breed in environments with elevated salinity (brackish-water).
In terms of care, Pom Pom crabs are moderately easy to maintain.
Like other crabs, they are omnivorous scavengers, that in addition to eating food items that collect on their claws, will also consume algae and detritus in the aquarium.
They readily accept high-quality foods that are rich in plant matter and occasional treats of protein-rich frozen-foods such as bloodworms, as well.
Pom-pom crabs have a generally peaceful demeanor towards snails and most fish, though they may go after dwarf-shrimp and very tiny slow-swimming fish.
To keep both your fish and crabs safe and happy, keep your critters occupied by adding plants and other verticle objects for them to climb and perch on.
They also love to hide quite a lot, so caves, rocks, and crevices will go a long way in making your pom-pom crabbies blissful😁.
I have not met many aquarists with much experience keeping panther crabs (or any crabs at all), but most sources I’ve researched indicate the critters are fully aquatic or will at least survive prolonged periods underwater.
However, similar to pom-pom and Thai micro crabs, it’s still a good idea to provide your panthers with some land area in the form of rocks or wood jutting out of the water. This will give them an option to emerge from the tank if they choose to.
In the wild, panther crabs are found on the Indonesian island of Sulawesi, concentrated around Lake Malano.
Their colors range between yellow, light-orange, and brown, with red markings and rosettes, with bodies that grow to between 1.5 and 3 inches.
For the best success keeping these crabs, add them in water that most suitable replicates their natural environment, including tropical water temperature and a moderately alkaline ph.
Panther crabs are omnivorous and eat a widely varied diet. They make good janitors as they will consume leftover scraps of food, algae, and detritus in the tank.
Store-bought foods like frozen brine shrimp, algae wafers, fish or shrimp pills, and flakes are another great way to supplement your panther crabs' diet.
Matono crabs are very stunning crabs with bright-purple bodies and white pigmented joints and eyestalks.
They are fully aquatic and not mainly dependant on a source of dry land, though they are not afraid of and are capable of leaving the water if an adequate ramp is available.
The crabs often reach 3 to 5 inches and are among the very few that will reproduce in a fish tank if correctly maintained.
Matano crabs are omnivorous scavengers by nature and are not picky. The critters will eat all sorts of food ranging from dead fish to decaying organic matter and algae.
If you need to feed them store-bought food, frozen options such as bloodworms, shrimp pellets, and calcium supplements will suffice, though you may want to go slow on fleshy-protein-rich diets.
To keep the crabs healthy and happy, with the possibility of adding them with tankmates, put them in a 20-gallon aquarium. Also, remember to create a lot of hiding spots with rocks, caves, and plants.
The Matano crabs are known to be excellent climbers and escape artists, among other exceptional traits, so either put a lid on your fish tank or keep your water line low.
#4&mdashThai Micro Crabs
Thai micro crabs are tiny, fully aquatic freshwater critters native to Thailand, where they live amongst hyacinth plants in only one river.
With attractive spotted patterns and lively personality, these tiny filter-feeding crustaceans make ideal additions to freshwater aquariums.
Thai micro water requirements are akin to those of most tropical fishies kept in home aquariums and are sufficiently nourished by algae, biofilm, or decaying plant matter in the tank.
However, in less mature aquariums, feeding them high-quality food with plenty of plant matter is recommended.
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Happy Fish Keeping.