Parathelphusa pantherina Biotope Aquarium      6/15/14
Hello, I've emailed you before and have had great service from you and you seem to know your stuff, so I thought I might run a few things by you again to see what you thought.
<Fire away.>
I am planning a biotope aquarium based on Lake Matano with the prime species being Parathelphusa pantherina (Panther Crab). I have had some of these before and have learned quite a bit and hope to succeed in breeding them this time.
<Cool.>
Last time I kept them, one was a female and released her pheromones in a too small of an aquarium and drove the males crazy. Needless to say, I found her limbless and she didn't make it.
<Some potential to separate them is surely a good idea, e.g., with egg crate. Do read on similar problems with cichlids.>
Anyways, I plan to keep them in a DIY acrylic aquarium measuring approximately 74 inches by 52 inches by 18 to 20 inches tall. I plan on housing three trios in this aquarium (trio = one male, two females). I've
done the math and this should leave plenty of space for them.
<Let's hope the crabs understand the maths too. Seriously, the hobby's track record of keeping amphibious crabs together is very poor. Many were shipped in soap boxes once upon a time, singly, so they couldn't interact with any others. During moulting they are all especially vulnerable, because a moulting crab is defenceless and viewed as an easy meal for any other crab. In the wild moulting crabs use deep burrows or something else to hide in.>
It's recommended you have one square foot of surface area to each inch of crab, so for these crabs being three inches, they need approximately three square feet of area each.
<While this recommendation sounds good, I suspect surface area is less important than topology. A crab isn't going to ignore one that's an inch outside "it's" square foot. So while providing space is important, you
probably also need rockwork, caves, 3D climbing structures and space above the waterline. This latter is important. A crab feeding on land can't see one below the waterline, and vice versa. I'm no expert on crab behaviour, but I'd also suspect they have different sets of behaviours used above and below the waterline because the predators, resources and stresses will be different.>
In the aquarium I have planned, this leaves just enough room for all nine crabs. I plan to replicate Lake Matano as much as possible including aquarium inhabitants but as of yet have not researched what other species of aquatic life are endemic/native to the lake, but I am open to suggestions (fish spp, shrimp spp, maybe some good substitutes).
<Snails and shrimps are definitely crab food, so a non-runner. Fish will be highly risky, as ever with crabs. While these crabs aren't fish predators, they are fish scavengers, and if a crab comes across a sleepy fish or manages to corner one... we'll, that fish becomes dinner. One crab might be tenable with a bunch of (initially inexpensive) fast moving midwater species along the lines of big barbs, but the more crabs, the less peace the fish will have. I think you're trying to do too much here. Breeding will require one set of criteria: potential to isolate "picked on" individuals; easy cleaning to reduce bacterial and fungal infections of eggs; countless hiding places to break up lines of sight; and some degree of flexibility so you can change the tank decor as needed when the unexpected happens. A biotope aquarium is designed for aesthetics, usually as a caricature of a particular place or habitat. That tends to force you to decorate an aquarium in a way that is less easy to maintain, rearrange or divide up with egg crate.>
I hope to create as much of a fully sustaining ecosystem as possible in all future aquariums but will be prepared to intervene if necessary.
<Do read "Dynamic Aquaria" if at all possible; the science behind microcosms that sustain themselves has been done, is extremely complex, and for home hobbyists, overwhelming. That said, if you're prepared for the extra cost needed for a biotope aquarium (e.g., in optimising plant growth) and stock the tank very lightly (understocking is virtually essential) then you can create tanks that more or less manage themselves in some regards, such as algae control and even population if the fish or shrimps breed.>
I know you recommend housing crabs alone,
<With good reason.>
but I feel confident about what I am embarking on.
<Which is fine. But have a Plan B.>
I plan to use driftwood with some sticking out of the water so the crabs can climb on them if they want, some sort of sand (open to suggestions)
that is natural-like, and rocks (what kinds of rocks are in Lake Matano?).
<No idea! But use neutral rocks regardless, such as granite or slate since the water isn't especially hard.>
I am open to suggestions on my setup. I will not be putting anything near the edges for them to climb out of the aquarium (to help prevent fatalities).
<Wise.>
I will have a sump with heaters and plants for filtration.
<How will you keep the crabs out of the sump?>
A drip system will continuously cycle my aquarium to help reduce concentrations of hormones and prevent need of water changes (water will be dripped into aquarium and excess overflowed out through the sump).
<Unless the hormones are diluted with fresh water, and old water continually leaves your aquarium (and sump) for the drains, hormone levels in the tank will not go down. Honestly, I suspect managing crab behaviour this way is dubious. Indeed, I can't find anything on Google Scholar about Parathelphusa hormones. Is this something brewed on the Internet or some cutting-edge scientific research? All the crustaceans I've ever worked with have been visually-oriented animals that use body postures, claw waving and so on to communicate. So while Panther Crabs aren't nearly as lethal as, say, Soap Box/Rainbow Crabs, I'd still be focusing on ensuring a complex, 3D habitat with lots of objects breaking lines of sight, as well as plenty of suitable caves and burrows. Might end up looking less like the Lake
Matano, but would nonetheless be more suitable for keeping crabs in numbers greater than 1 specimen.>
Any suggestions? I appreciate you answering my questions and giving me advice on how this may or may not work out. Have an awesome day!
<Most welcome, Neale.>
Re: Parathelphusa pantherina Biotope Aquarium      6/19/14
So, I've decided to play it safe and focus on breeding the crabs first. I was reading up on a few things and came across your article about the freshwater deep sand bed. I was wondering if it'd be possible for me to set up one of these in a 10 gallon aquarium with one crab?
<Do you mean Deirdre Kylie's article?
http://www.wetwebmedia.com/ca/volume_7/volume_7_1/dsb.html
Doable, yes; worthwhile, debatable. A 10-gallon tank isn't especially large; the standard US version has a depth of 12 inches (about 30 cm).
Since you need 3 inches (at least) for the DSB, that leaves you relatively little for the water. It would certainly be fun trying, but think about any potential compromises you might have to make. I will also observe that crabs are almost always deposit feeders to some degree, which means they sift mud and eat any organic material they find. That's great in the wild, but will make a full-featured DSB somewhat less easy to create because things like worms and micro-crustaceans are going to be eaten.>
I plan on putting one crab in a 10 gallon with a 10 gallon sump.
<Ah now, the DSB in the sump *would* work, and could work great.>
The 10 aquariums would be connected to each other via an overflow in each aquarium.
<Sounds good.>
I may put in a water bridge, but just thought of this as I was typing this, so I'm still undecided on this. Anyways, what are your thoughts on the deep sand bed? Will the crabs burrow too much?
<Not sure these are deep burrowing crabs, and don't look like them, but most crabs do usually move about the top layer of mud as indicated above. I have no idea how much movement this species is likely to carry out, but I'd be aware of the possibility.>
Should I just have it in the sump? I plan on a three inch deep substrate for the DSB, and in case the crabs want to burrow. Thank you for your time.
Have an awesome day!
<Breeding projects are most easily done in the cleanest possible tanks for various reasons including minimising opportunistic bacteria and making it easy to see eggs/fry. If this was me, and breeding was my goal, I'd probably look at plain tanks, sponge filters (great for aufwuchs growth) and easy to clean climbing surfaces for the crabs. But if breeding is a welcome spin-off rather than the prime goal, then a "freshwater reef tank" project with the focus on microbial life could be very worthwhile, and might provide opportunistically useful food and niches for crab eggs/zoea.
I think you will need to consult Google Scholar to find out whether Parathelphusa spp have a marine larval stage; I do not know if they do (many amphibious crabs do) and that may be a complicating factor that
requires collecting eggs, transferring to brackish then salt water, and rearing accordingly. Has been done, rarely, in the case of some freshwater Gobies and Amano Shrimps, but obviously a major project. Cheers, Neale.>