Attempting to Breed Microcrabs

[jasonpatterson]

Originally Posted by msjinkzd

I wanted to share this picture of how the snuggle intothe roots of floating plants. This is a narrow leaf java fern, but it is not attached to anything. I find the most crabs (by the dozens) tightly wedged into their roots.

I find mine in the roots of my red root floaters, even though they must have had to swim upward 6" or so to get to them. I've never seen them go up, but every morning there are half a dozen crabs hanging on up there.

[jasonpatterson]

It's been a bit since I updated this, but I have made some changes to my setup and hopefully that will help. I wanted a dedicated crab tank so that I could feed them appropriately and filter in a way that would not disturb the zoeas. The space that was available only permitted a tank that was 8" tall or so, so I decided to make a half-10 tank. I bought a 10 gallon tank from Petsmart, disassembled it entirely, keeping the bottom plastic frame intact, and cleaned all the glass. The size walls were cut to a bit more than 6" and then I reassembled the tank. The bottom frame and the construction of the tank allowed me to flip the pieces so that my cut edges were downward and any unevenness or differences in height were masked. The final result isn't perfect, but it's not terrible either. I added about 1.5" of topsoil to the tank and filled it up. While it cycled a fair bit of tannins came out of remaining wood chips in the soil, and I figured out a way of doing water changes that doesn't disturb the substrate at all. Again, it's topsoil only, so until it had grown a bacterial mat that fused the surface it was very easy to disturb and cloud up. I also added several maple leaves for cover and extra surface area.

I didn't want any current to speak of in the tank, so I went with an air powered corner filter. I filled the container with biobeads, modified it to use an airstone (which makes it much much quieter) and added an elbow to the outlet to force the water to the side as it exits the filter. As a result the filter is very quiet, produces almost no current, but does a good job in the biological filtration department.

I bought the double bright LED light from Marineland. I'm not thrilled with it, but it seems to be doing the job, suspended about 4" above the water's surface. The light it provides is in very tight cones, so it acts like a set of spotlights. Apparently the longer fixtures don't have this problem, but the one that fits a 10g definitely does. The only plants I've got are red root floaters, and the roots extend to within an inch or two of the dirt at the bottom of the tank in a few of the larger plants. They're growing, and flowering even, with this lighting, so hopefully it does the job in the long run.

Finding and catching the crabs from my main tank has been the biggest challenge thus far. I've had a population explosion in both my bumblebee and yellow shrimp and they don't leave a lot for the crabs to eat. I've lost 3 or 4 crabs over the last two weeks, far more than in earlier periods. I don't want to disturb the tank too much, so thus far I've only been able to nab 6 of them. It's a mix of 2 males and 4 females so far, and one of the females was berried. She hatched out just this evening, which was really cool to see. She was hanging from the roots of one of the RRF and flapping her tail, spewing out the zoeas into the tank. I'm hoping that the tank is able to support the zoeas, but it's fairly new, so there really isn't much for them to feed on yet. Lots of bacteria and stuff like that. We'll have to see how it goes.

[Fishfur]

I'm thrilled to find this thread. I obtained six of these charming little crabs just a short while back, and have already lost one, no idea why. No idea whether it was male or female either. I have seen one feeding in the roots of a water sprite, the others I have not seen at all. There's a large piece of driftwood in the tank, a 5 G, and they seem to hide under it. They are nearly the same colour as the wood. I've been using the tank as a brooder for Ghost shrimp and currently have a number of one/two week old shrimplets in there, plus one Blue Claw Whisker shrimp who is much to canny to catch.

Moon sand substrate, loads of large frogbits, giant duckweed and water sprite, so lots of hanging roots for them. Been feeding very sparingly, as there is little mechanical filtration. Filters are a sponge, inside corner and small Fluval power unit. Being concerned about shrimp larvae being sucked into filters, I covered the latter two filters with 100 micron filter felt and stitched it on, so it gathers only microscopic detritus on the outer cover for the most part. Thus most of the filtration is biological. I do the odd WC, usually with a air hose stuck in the sponge filter uplift, to avoid sucking up shrimplets. I recently learned there are amphipods in this tank too. Don't really mind, they are kind of cute, and do not seem to be able to catch shrimplets.

So far, I have not been able to observe the crabs enough to have a prayer of sexing them, but I am most anxious to attempt to raise any eggs that may hatch, assuming I have both sexes. I'm going to read the papers that are linked here soon as I finish this. I too was wondering about brackish water for the eggs. While my Ghost shrimp have done fine in FW, my Whiskers have not, and I was going to do a brackish tank for them, in hopes they are similar to amano shrimp. They and the ghost shrimp are certainly breeding well in my 30 G main tank. All my tanks are fairly heavily planted at this time, with either eco complete or moonsand substrates.

Local water is quite hard and tends to a high Ph, close to 8 as it leaves the tap. I use mainly conditioned tap water, and so far, everybody seems quite happy, but the crabs are in the small brood tank, which tends to become more acidic with time and because I do fewer WCs. I think likely the big piece of wood in a small volume of water is doing the acidifying.I top up with distilled water, but I do WC with tap. The shrimp so far seem not to care about some fluctuations in their conditions, but I worry about the crabs. I have another tank ready to go, also 5 G, no fish, but it also with a few amphipods.

I have been feeding an assortment of sinking crustacean pellets, algae tabs, liquid invert food, meant for corals, green water and finely powdered spirulina mixed in water, mainly to feed the free swimming larval stages for the Ghosts. I feed those last three to my clams as well. There are snails in all the tanks.. pond, mystery, horned and zebra nerites. I thought it might be fun to try hatching some nerites in a brackish tank too, though to date I have zero experience with salt water of any kind.

If anyone on here has any suggestions on what conditions I should aim for in my new crab tank, please let me know. However, since it is difficult to fight the way the local water likes to be, and I am not in a position to afford RO water, I am hoping they are able to adapt to what I've got. I have a small distiller, gives me a gallon a day when I run it, but it's not enough to keep a tank going non stop without any tap water being used. Could maybe do half and half if need be. I do use it for top ups to avoid making the water any harder than it already is.

Any and all suggestions most welcome. I would be beyond ecstatic to succeed in breeding crabs. Just having the Ghost shrimp morph and survive was a huge thrill as I am quite new to shrimp keeping too. I later found better than half a dozen Ghost shrimp survived in my 30 G tank as well, despite the hazards of the filter, the pump, the danios, kuhlie loaches and three dozen odd shrimp that are also in there. Filtration may not be as big a hazard as I feared it might be, but I'd still make every effort to prevent any eggs or larvae from accidentally being sucked in. There is even 55 micron felt available to make filter covers with. In my main tank, all I did was make sure to stuff some intake grates with coarse sponge cut to fit, to prevent baby shrimp from getting sucked in, but I didn't cover the slots on the lid, only the ones at the front and lower edge. I must confess that the half dozen survivor Ghosts are likely all that's left out of, probably close to one hundred eggs that were let go in there, so it's not a great rate, but I was amazed that any managed to live.

Also, any suggestions on how to actually see my crabs without stressing them too much. They've been in their tank only for a week, so I hate to bother them just yet, but I want to see if I can discern the sexes and also whether they're eating. Would simply raising the piece of wood onto a couple of small rocks be likely to help me see them without taking away their hiding places ? There are no rocks to speak of in this tank, just the sponge filters and the big driftwood piece that goes from the front to rear corner on the diagnonal. Has a lot of ferns tied to it and some mosses, but not much has had a chance to become solidly attached.

[jasonpatterson]

Best of luck raising the larvae. There's something missing that nobody has quite figured out yet.

My crabs became a little less shy over time, but with a good sized piece of driftwood, you're not likely to get all of them out. Feeding something like bloodworms or mysis shrimp can lure them out, especially if you do it right before lights out and watch closely afterward. They are quite shy though, so there's not a lot you can do. You might be able to use rocks to lift it up, but they'll climb under the rocks as well.

Sexing the crabs is fairly easy once you get a look at them. The males have a tail that is shaped like a v, and the females have a tail that is shaped like a broad U. If the tail is yellow, the crab is berried.

[jasonpatterson]

An update on my current batch of zoeas:
I had a second berried crab that hatched out as well, and a swarm of zoeas to accompany the event. After about an hour, neither batch of zoeas was visible. I know that when I kept them in a small container they went straight to the bottom and stayed there. In this tank there is a lot of cover for them on the bottom, and they may be burrowing as well. I haven't seen a single zoea from either batch since almost immediately after hatching. It's frustrating, because there's really no way to know whether what I'm doing is working without seeing a baby crab some day.

I really don't expect the current lot of zoeas to live anyway, as the tank is awfully new and there isn't a lot of microflora/fauna in the tank.

[dougolasjr]

Any update?

[jasonpatterson]

Complete and utter failure on all fronts thus far. I'm moving in the next year or so, so I'm trying to avoid getting anything new during that time. I've been losing a crab now and again as time goes by, and my population is dwindling. I'm going to give it another serious go once we move, if all goes as planned.

[dougolasjr]

Well that's unfortunate. I was hoping to hear good news.

[DannyDapper]

Any updates on your attempts to breed them?

[MABJ]

Originally Posted by jasonpatterson

Complete and utter failure on all fronts thus far. I'm moving in the next year or so, so I'm trying to avoid getting anything new during that time. I've been losing a crab now and again as time goes by, and my population is dwindling. I'm going to give it another serious go once we move, if all goes as planned.

I was happy to see this thread.

I've read everything I can online about them. The best I've gleaned from advanced German breeders is that they found some correlation between light and survival. Also being that they're filter feeding, I'm sure a food has something to do about it.

So my assumption... Which may be a stretch.. Is that light is their orienting factor. They stay close to the surface to (in their home river) get a micro algae or micro particle of food which they catch as they move down the river quickly. We have yet to be able to replicate this unfortunately.

Nobody has been able to bring them past day 9. Other than miracle baby by Rachel? That's an anomaly I've never heard of. It only takes a few days for them to grow out of their free floating form, like your amazing pictures documented.


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[blacksheep998]

Originally Posted by MABJ

I've read everything I can online about them. The best I've gleaned from advanced German breeders is that they found some correlation between light and survival. Also being that they're filter feeding, I'm sure a food has something to do about it.

So my assumption... Which may be a stretch.. Is that light is their orienting factor. They stay close to the surface to (in their home river) get a micro algae or micro particle of food which they catch as they move down the river quickly. We have yet to be able to replicate this unfortunately.

Probably a stupid question but has anyone attempted raising the babies in green water?

I'm not sure how to replicate the water flow, but maybe if they're literally swimming in food they'll be able to survive.

[MABJ]

Originally Posted by blacksheep998

Probably a stupid question but has anyone attempted raising the babies in green water?

I'm not sure how to replicate the water flow, but maybe if they're literally swimming in food they'll be able to survive.

Yes. Rachel attempted, I believe, to raise several larvae in green water. I'm pretty sure she had one stray baby make it but that was in her normal tank. So I don't know what miracle happened there.

Trust me I don't know the answers either. Otherwise I'd be making a killing off breeding and selling these guys.


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