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Linden

Amarinus Laevis Care and Breeding

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Linden
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.

Screenshot_20190724-221155_Gallery.jpg

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. 

Screenshot_20190724-222027_Gallery.jpg

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. 

Screenshot_20190724-222222_Gallery.jpg

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. 

Screenshot_20190724-222324_Gallery.jpg

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. 

Edited by Linden
Significant additions and revisions.
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Rare Aqua

Great post, do you have one on A.lacustris?

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sdlTBfanUK

A great and fascinating article with lovely pictures!

Simon

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Linden
On 7/25/2019 at 5:35 PM, Rare Aqua said:

Great post, do you have one on A.lacustris?

I haven't kept A. Lacustris. Really want to breed them also. 

Edited by Linden
Information assimilated into original post.
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waffle

Awesome writeup!!!!

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Linden

Hi everyone. I have done a significant rewrite adding more information and techniques. Some of which is likely unknown by many. 

Enjoy. 

I plan to add more photos in the future. Winters end will see a big remake of my breeding tanks/racks. So those updates will be months away. Much else to do first. 

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Rare Aqua
On 7/27/2019 at 2:01 AM, Linden said:

I haven't kept A. Lacustris. Really want to breed them also. 

Hey, I dont want to brag but i believe i was the first to sell TANK raised A. lacustris, i have been breeding them for 3 almost 4 years now an did a very old write up about them, similar with you there is a lot i need to add to the initial care post, all in good time however. and a heads up i do sell juvies but once a year and have sold out as of now. Email me for more information 

zebradanio88@hotmail.com 

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Linden
2 hours ago, Rare Aqua said:

Hey, I dont want to brag but i believe i was the first to sell TANK raised A. lacustris, i have been breeding them for 3 almost 4 years now an did a very old write up about them, similar with you there is a lot i need to add to the initial care post, all in good time however. and a heads up i do sell juvies but once a year and have sold out as of now. Email me for more information 

zebradanio88@hotmail.com 

I totally don't consider that a brag. I'd love to get into A. Lacustris. Will email in time. 

 

I think I was the first I have been able to tell to sell tank raised A. Laevis. Even if not. I want more to breed them. Hence me trying to share all I can. 

 

I'm going through a load of creature room moves and at this rental, The back shed (aspestos wall) I'm closing down but getting a new bigger double breeding rack ready for when I can start again and better than before. 

Today I brought in about 267 females 9ish mm carapace size up to 14mm, from those tanks into temp in house tank racks. But only got 5 males excluding the original breeders. 

 

I plan on adding more photos over the next month. And even more when I remake the new breeding racks come summer (or once the shed dilemma is resolved). 

 

Here's a teaser photo of over 100 in my hand as I worked through them ensuring all males were seperate. 

 

Screenshot_20190803-164450_Gallery.jpg

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jayc

I'm glad we have some experts here on fresh water crabs.

Edited by jayc
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Rare Aqua

Jeez that's a lot of crabs!!, Linden sure is the A.Laevis King and I the A. Lacustris King 😏

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Crabclaw
On 8/4/2019 at 1:25 PM, Rare Aqua said:

Linden sure is the A.Laevis King and I the A. Lacustris King 😏

U guys seem to be the ones to ask questions to then. I've got a 110 L, well planted, stocked with some tt shrimp and a bunch of nano fish. I also have a pair of apistos, and they've been pretty nice to the shrimp so far, haven't seen them picking on the tts (just my poor BNs when they were added). If I want to keep crabs in this tank, should I go for A. lacustris, and risk never seeing them, or them getting picked on/eaten? Or A. Laevis and risk them hurting/hunting the shrimp... or should I get a 10-20 L and keep a. Lacustris and shrimp? (I'd like to give breeding them a go as well, at some stage)

Either way I want some crabs bad! Could either of u guys sell me some, as I haven't seen them anywhere else. 

Cheers, 

Crabclaw

Edited by Crabclaw
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Rare Aqua

Hello, I'd go for A. Laevis in that case just as they are larger, i would only keep A. Lacustris with shrimp, Snails or REALLY small nano fish. Apistos would eat the crabs and if not the 100% eat all their offspring

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Crabclaw

Thanks rare aqua, I’ll go for them then! Will the laevis eat my shrimp?

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Rare Aqua

Its subjective but ive found they DID predate on my shrimp even with a lot of food being fed daily, so going off my own experience they will predate on the shrimp, probably not to the extent of killing them all however

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Crabclaw

Hmm, ok, I’ve only got 8 shrimp in my tank rn, so sounds a little sketchy. If I set up a seperate tank for a. Lacustris n shrimp would u be able to sell me some?

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Crabclaw
On 7/24/2019 at 10:24 PM, Linden said:

shrimp and fish safe in general.

Linden, what's ur opinion on keeping A. Laevis with shrimp? Do you have problems with predation in your tanks? Do you think it's possible to breed both together, or even just shrimp when with A. Laevis?

Also, would you be willing to sell me some?

Cheers

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Rare Aqua
6 hours ago, Crabclaw said:

Hmm, ok, I’ve only got 8 shrimp in my tank rn, so sounds a little sketchy. If I set up a seperate tank for a. Lacustris n shrimp would u be able to sell me some?

I have sold out of all my juvies for this year

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Crabclaw
6 hours ago, Rare Aqua said:

I have sold out of all my juvies for this year

Oh bummer. When do you think you'll have more available?

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Linden

Hi. I've kept A. Laevis in many tanks with stable shrimp breeding colonies. Not a rare sight to see a shrimp riding around on the back of a large crab. Eating the collected particles from the crabs fine hair. 

While the crabs will eat dead shrimp. I can't say I've seen them predate on young or adult shrimp. However if the opportunity arose, I wouldn't be surprised if it took a failed swing at a shrimp. The crabs are just so much slower than shrimp. 

In A. Laevis breeding tanks I have often breed glass shrimp in the same tank. As they both have a free floating stage. 

In normal aquariums (not A. Laevis breeding tanks) that have shrimp. The shrimp still breed. I don't witness any predation. And I have 3 tanks with crabs and shrimp (plus oddball fish like eels and elephant nose) in my bedroom which I spend loads of time staring into. 

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Crabclaw
20 hours ago, Linden said:

I've kept A. Laevis in many tanks with stable shrimp breeding colonies.

Ooh yes that's good news! I have apistogrammas in my tank though, and jayc said that they would likely predate upon the crabs, picking at the legs and such bc apistos have a fetish for crustaceans... Do you agree with this, or think it would work? How on earth do you keep eels with shrimp?! Very impressive.

If you believe that they would be fine with my semi-aggressive apistos (the male of which is being considered as a suspect for the murder of 5 rocket killies who have gone missing) would you consider selling me some A. Laevis?

I also sent u a pm regarding most of this a couple of days ago.

Cheers!

Crabclaw

 

Edited by Crabclaw
adding important information

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Linden

Photo of a 5cent coin sized females 'flushing/cleaning/breathing' her eggs. Can really only see her abdomen open from this angle. 

Have a video. Just need to make it smaller file size. In a few days. 

20190829_193714.jpg

Closing down another tank with about 100 female crabs in it tonight. 

Eager for summer new breeding rack city setup. 

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sdlTBfanUK

Great photo!

Simon

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Rare Aqua

amazing photos, my F2 A. lacustris are almost at their pubescent moult! so im expecting some berried females in a couple of months😏 

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      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


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