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Australian Freshwater Crab Freshwater crabs can be found in the tropics and subtropics in most parts of the world. Out of a total of 6,700 species , there are more than 1,300 described species of freshwater crabs,and many more currently unknown to science. The IUCN (International Union for Conservation of Nature ) Red List has assessed all described species as “ data deficient”, as data on their ecology, reproductive biology and habitat requirements is lacking. (Austrothelphusa Transversa) The majority of species studied to date tend to occur in small geographic areas, have poor dispersal abilities and low fecundity (the ability to produce an abundance of offspring) thus making them highly susceptible to land use alterations, river regulation changes and climate change. Scientists in Australia are investigating the biology and ecology of our remarkable freshwater species in the tropical regions of northern Australia and the Torres Straits. Very little is known about many of the far northern species, however science has discovered that they have an amazing lifecycle, these crabs will dig tunnels in the creek banks at the end of the wet season and spend the hot and dry times in a prolonged state of torpor/dormancy, emerging again at the onset of the next seasons rains presumably to feed and reproduce. Females of the species A. Transversa have been documented carrying their young under their abdomen underground during the dry season and when the wet season arrives they will leave their mother growing up quickly before the next dry season. A.Transversa The most common species of freshwater crab found in the aquarium market in Australia are the Holthuisana sp. (Austrothelphusa) There are several sub species in this order: A. Agassizi A. Angustifrons A. Receki A. Tigrina A. Transversa A. Valeatula A. Wasselli With the most common on the market being A. Transversa and A. Agassizi : A. Agassizi (Freshwater Brown Back Crab) CARE: The two species A.Agassizi and A.Transversa are by nature amphibious and should be provided with an “Island” where they can leave the water at will . It seems they require atmospheric air for their gills to operate properly. In nature these crabs frequent inland rivers and billabongs in northern Australia that dry up in the winter. Water Quality: Temperature: 18 deg C. to 25 deg C. pH: 6.5 ------7.5 General Hardness Soft /Moderate The freshwater crab can not survive for long in very acid water. Make sure their wateris free from ammonia,nitrate and copper. Feeding: A true scavenger, they will eat most types of sinking fish food, blood worms, fresh vegetables and sometimes aquarium plants. Colour and Varieties: The A. Agassizi ( Brown Back Crab) can come in a variety of colour patterns e.g with an attractive pale fawn colour, with a chocolate brown irregular band crossing from front to back of the carpace or even a tiger stripe pattern. While the Colours of A. Transversa is mainly a shade of brown from yellowish to deep redish. Housing: Both species are great escape artists and can easily climb the silicone in the corners of most tanks. I have had them climb up air hoses and the water pick ups for the filters. They are fairly peaceful and can be trained to come to your fingers for food. If kept in a community tank ensure that there are no slow fish as the crabs are not adversed to a little fresh fish in the m Disclaimer: A. Transversa The information provided here is of a general nature only. Citation: The IUCN red list Dr Nathan Waltham: Ecology of Freshwater Crabs in Tropical northern Australia View full article

Hello. I've written the following based on my own time scouring the internet and then personal experiences with my mud crab Gaston. Mud crab aquarium care. Tank setup: Minumim 4ft aquarium. A 4x2 ft much better. Like with turtles, larger footprint is important. Not so much how tall the tank is. Seriously big crabs. Be open to having a 6ft aquarium if you plan on risking tank mates (other than glass shrimp, snails and tiny fish). Unless your in Western Australia, you'll get Scylla serrata aka Green mud crab (not named green for being green. Can be brown and blue also). They can grow up to 30cms and 2.5kgs with 20cm claws. Have a cycled aquarium with brackish water about 1.006-1.010 SG. Heated 19-25°c. PH around 7 or higher. Harder water is important. Crushed coral can help balance out soft tap water and the use of driftwood. Breaking up some cuttlefish bone in the water column is important. Calcium for shell development. They are from estuaries. So have a great tolerance for temperature and salinity fluctuations. Decent filtration is a must as they are exceptionally messy eaters. I recommend a sump. The crabs are very strong and can snap heaters, damage power cables and move tubing. So a sump for the hygrometer and heater helps, with the benefit of the overflows and returns being secure. Also clamps to hold parts in place. Pvc tubing can be used to protect power cables and keep equipment protected. The lid needs to be very secure. With only small gaps and also weighted down. The crabs are strong and can easily lift glass. Some additional glass pieces on the lid to keep it down is recommended. The crabs will want to get their mouths above the water line periodically. So don't fully fill the aquarium. About 20cm deep. Deeper depending on if you have driftwood or rock climbing areas so it can still reach above water line. Note: ensure all rocks and driftwood are very securely and purposefully positioned. Remember they are very strong and can move unsecured rocks and driftwood. Poorly placed rocks could be moved and break the tank. Using larger rocks and wood is safer than easier to move small pieces. Sand as a substrate is best. 6cm or so deep. Mixed with some crushed coral and aesthetic gravel. They sift through sand for scraps plus it will help fill cracks between rocks n such to secure them even more. They will eat plants. So not a great aesthetic addition. Don't put strong lighting on the tank. The crabs like to hide. Plus they'll grow algae over their carapace under too strong and or long exposure. Glass shrimp will help keep this down. Aquiring: Can be bought from a fish market. Sold as live food. About $50 per kilo. A standard mud crab will be about 0.8-1.4kgs. Google how to pic a healthy mudcrab. You want to select the healthiest male you can get (not the biggest). Note. They'll all be male. Transport in Styrofoam box or esky with a little ice. They'll wrap it in newspaper. When home. Unpack it (keep the claw string on) then move it into a large container or tank with no water for about an hour as they 'defrost'. Remove the claw holding string as you move into their aquarium. Have a friend around to help with lid for safety reasons. Feeding: They are scavengers and eat a wide variety of foods. They will make a big mess when they do, so some glass shrimp, Malaysian trumpet snails and a few tiny fish are beneficial for cleaning up the shower of food particles. My favourite foods to feed are small whole cooked tiger prawns and marinara mix from the deli. Some white fish cut into pieces then frozen. Repashy with added calcium (powdered egg shells or cuttlefish bones). Make big skeets in flat zip lock bags and freeze. Snap off a piece for feeding. Can also feed worms, clams, scollops, crab pieces, garden snails, plant matter (like excess Elodea from another tank). A varied diet is important. But most of all is getting plenty of calcium in their diet. The repashy +calcium or a similar diy mix with agar agar, calcium, seafood and added vegetables is gold. It might not take to eating well initially. I recommend using long planting tweezers. Carefully. Don't want them to grab the tweezers. You can train them onto eating by attaching a piece of meat or prawn to some cotton string. Jerk it around infront of him until he goes for it. Might take a few tries. Don't leave large pieces of uneaten food in the tank to spoil. Be very careful putting hands into the tank. They can go from slow to very fast moving in an instant. Here's my Gaston.

Fully Aquatic Freshwater Crabs Amarinus Laevis. Difficulty: Intermediate Max growth size: 2.5cm across carapace (shell width) Temperament: Peaceful. Safe with other animals that wouldn't attack the crabs (not suitable with large Cichlids or other large aggressive fish). If underfed. Might take advantage of already weak or injured nano fish or shrimp. Only heard of this happen very few times. They are great for eating snails. Don't eat plants, only decaying plant matter. Preferred water parameters; Temperature: 10-28*c can handle colder. Increase air supply in warmer waters. Great for unheated indoor tanks. General harness: medium to moderate. Just like with snails. Soft water isn't healthy for their shells. Harder, calcium rich water is preferred for healthy moults. Crushed coral, shell grit, crushing some cuttlefish bone and/or feeding them snails is recommended. Tank size and notes: If keeping only females. A group of 3 is a minimum. Otherwise they'll be less outgoing. The more in the group the more comfortable and outgoing they are. They have a small bioprint. While we do feed them. They also scavenge and break down food and detritus into easier to be filtered forms. Aiding in a healthy balanced ecosystem. 3-6 female crabs can be kept in a nano tank of 5 gallons (19 litres) given the tank has a filter. A standard 2ft tank (approx 14 gallons or 50 litres) can support up to 20 female crabs. I frequently keep more in less water but only when it's just crabs (plus some shrimp and snails). If you have a male. A larger tank is needed as males can be aggressive. Preferably doubling the above recommendations. For breeding tank details. See breeding guide write up. Planted tanks are preferred. Aiding in filtration, providing climbing areas for the crabs and decaying plant matter is bonus crab food. Reproduction: Difficult. Requires around a dozen adult females, a non aggressive male (rare) and an aged tank. They have a free floating baby stage similar to glass shrimp. The vast majority of this species are female. Males are quiet rare and violent to other males. Often with a harem of numerous dozens of females each. Feeding: Scavengers that love sifting through mulm and poop. Feed sinking omnivores pellets, sometimes algae wafers. Will eat all sorts of foods. Supplementing with live snails is fantastic. Smaller wafers and pellets (I use 1mm sinking pellets) are better than larger ones to reduce the chance of fighting over food. Pellets with added calcium are a bonus to shell health and moulting. Additional comments: A truely unique, uncommon species in the aquarium hobby. Lifespan about 2-3 years. They can survive in low end brackish water. 1.010 SG or less. Making a unique snail eating native that thrives in both fresh and low end brackish. Plant, shrimp and fish safe in general. Doesn't need or use above water area. Recommend using an air stone if not using air powered sponge filtration, to ensure enough dissolved oxygen in the water column for them. Especially in warmer, tropical tanks. Breeding Tank setup information: I have had much success with many types of Substrates and setups. As the crabs are very hardy. My preference due to being cheap and effective is as follows. Breeding these crabs I consider advanced. There are a few important, easy parts to the process that if skipped can lead to failure. Substrate: Back or side 2/3rds of the base plain River rock gravel (any natural gravel you have laying around is fine). Front or other side 1/3rd sand (play sand from bunnings is cheap and effective. Sprinkle of crushed coral over the substrate. Decor: Driftwood. Piles of larger lava rock pieces (Washed. Bunnings or landscape supply store real cheap). Dead coral rock if you have any is beautiful to use. (skip adding crushed coral if using this). Plants are highly recommended. The crabs don't eat plants unless it's decaying matter. Plants help with water quality but also add environmental enrichment for the crabs that love to climb on them and micro-organisms for them to feed off. I now add a tiny bit of marine salt to their breeding tanks as it slightly increases zoae survival rate. The added nutrients and minerals seems beneficial (however not required) for the free floating zoae. Filtration: Sponge filtration is best. It provides oxygenation for the crabs and can't suck up the free floating first form zoas the eggs hatch into. If using other filtration, a cheap sponge covering the inlet is required otherwise all new babies that float in the water column will simply get filtered out. Also if not sponge filtration. Adding an air stone is recommended. Since the crabs are true aquatic. They don't go above water to subliment oxygen if ever there's less than desired in the water. Equipment: A light on a timer is a good idea especially with plants. The algae build up is a food source. The best food source for the young is green water. Which takes some trial and error to get dialed in. A heater is not required. I've had them breed in an outdoor carport over Victorian winters. 5°c nights and under aren't rare. Size: For a breeding pack (1 male and harem of females) a 2ft tank is a minimum. However 3ft is recommended and definitely will be better suited for survivability. A 4ft would be fantastic, in which the male could have a breeding harem of numerous dozens of females. Life cycle: a single male will mate with his harem of females they'll form around 200 eggs when berried. After weeks of fanning and cleaning the eggs. The female will release them into a light water flow as the zoae hatch. These free floating first form young drift about just like glass shrimp zoae. Consuming nutrients, green water and dissolved calcium in the water column until they go through a moult into a fully form micro crab. About 1mm in size. These live amongst the pourus lava rock and in the mulm that should be allowed to build up. Going through numerous moults as they grow in size. Some won't survive moults, some will be eaten by adults (sufficient mulm and suplimentary feeding minimises this). Of one females 100-200ish eggs. Those that survive to adulthood are in the many dozens, not hundreds. The young are a common food source in the wild for micropredators. Of those few that make adulthood. Only 1-3 will be males from my experience. Many of the other males potentially eaten or fought each other at younger ages. When crabs reach about 6-10mm across carapace is when I remove them into grow out tanks. New young males of this size need to be removed to seperate tanks with a dozen same size females, as they will likely fight other males to the death for the right of ownership of a harem. There are rare instances where the lionesses will kill their alpha lion if he isn't sufficient or doesn't continue to prove himself worthy. Similar can rarely happen with the crabs. So having same sized male/females is important. Especially at a younger age when the males are still learning how to be alpha. On the other hand. A large aggressive male with a harem of young females can all of a sudden go crazy and kill them all. A balance between the sexes is important. In the wild. The insufficient male or the weak/young females would simply be kicked off the rock and have to search for another group. To replicate this we would need very large tanks or ponds to avoid constant civil war. I am eager to assist any willing to try and breed these. I would love for them to be far more readily available to the hobby. Demant far outweighs what one can breed themself. 1st pic is a male standing on a ball of females. When moving large groups into grow out tanks, the crabs will form a ball made up of dozens. 2nd pic shows a appropriate mix of Substrates and tank setup. Has all the right components. Illustrating that breeding tanks don't have to be dull and unsightly. 3rd pic. A stunning male. Showing their magnificent claws. Note the messy wood. Mulm is your friend when breeding these. The adults sift through for food, the young live amongst mulm, eating it and biofilm. Breeding glass shrimp of other zoae stage shrimp in the same tank is a perfect match. 4th pic. A close up of the tank in the 2nd pic. Showing a male and some of his harem of females at feeding time. The male eats first and keeps the females in line and waiting for their turn to eat the pellets that fall near him. Waving his claws around at them as they approach. The crabs like to congregate on a single large rock. Especially on the underside of it out of the light when they're not scavenging for food. Porous rock is better so they can grip and for the young crabs to hide in from the adults that might eat them if hungry enough.