Red Claw Crabs, Red Thai Crabs, Sesarma Bidens...help!

[sophiegackowski]

Hi everyone,

I'm relatively new to this forum: and relatively new to keeping crabs!

Basically I got a tank from my brother a couple of weeks ago, (he kept fish for a short time when he was younger but wasn't successful at 14...) and set out on my quest to set it up. I scrubbed it spotless, using only water, and got some gravel - cleaned it for two hours! I bought two little bottles of chemicals to begin cycling the tank, and before I knew it the water was crystal clear, at 26 degrees celsius, and relatively humid. I have been regularly visiting many local fish stores, and decided upon setting up a species tank. I researched and researched and have fallen in love with these red thai crabs (sesarma bidens). I bought some oxygenating plants (which they will no doubt eat) and ordered my crabs on Friday. Expecting them in my lfs on Thursday.

I have read that they like brackish water and certain conditions so I have just ordered:

1 Brightwell Aquatics Iodion 250ml (I hear iodine is good for them when moulting)

1 Brightwell Aquatics Calcion 250ml (I hear calcium is good for their shells, rejuvenation etc)

1 API 5in1 Aquarium Test Strips (for nitrites, nitrates, ammonia, GH and KH levels)

1 API Ammonia Test Strips

1 Pack of Red Sea Salt 60 litres

1 Aqua Vital 80353 Chamber Hydrometer

I know this post is very long but I really want to give these critters the best chance they can have, and have heard terrible stories from people keeping them in freshwater etc. I may not be receiving this order until thursday or friday, so could I keep them in fresh water with a little sea salt from a local store until I receive my marine salt (only be a matter of 24-48 hours)? Can I add the salt to the already cycled water or should I start again? Does anyone know the accurate readings I should be getting from the test kits and hydrometer for these invertebrates? I have also got some rocks in my tank stacked to create a land area, and water only filled to around half way up. I have a 36 litre tank also, so how many could I have in a purely species dedicated tank?

Any help or advice would be invaluable.

Thanks,

Sophie

 

[nmonks]

I may not be receiving this order until thursday or friday, so could I keep them in fresh water with a little sea salt from a local store until I receive my marine salt (only be a matter of 24-48 hours)?

Yes.

Can I add the salt to the already cycled water or should I start again?

Yes, provided you don't dramatically change the specific gravity. Going from SG 1.000 (i.e., freshwater) to SG 1.002 or 1.003 in one fell swoop will do no harm at all. After that, by all means raise the salinity one "point" up the scale (1.002 to 1.003, etc.) every couple of weeks. SG 1.005 is fine for these crabs.

Does anyone know the accurate readings I should be getting from the test kits and hydrometer for these invertebrates?

Couldn't matter less. They're euryhaline and will adapt to variations in salinity much better than your filter bacteria. Aim for a salinity of 1.002 to start with, and 1.005 within a couple of months. Hardness and pH will take care of themselves, assuming you're using marine salt mix.

I have a 36 litre tank also, so how many could I have in a purely species dedicated tank?

They are sometimes rather aggressive to each other, so don't be surprised if there are casualties at moulting time. I'd set aside a good 10 litres or so per specimen, and make sure there were ample hiding places (caves, in particular) so crabs could moult safely.

Cheers, Neale

 

[sophiegackowski]

Thanks Neale, that's such a relief to have a straight answer!

As for calcium and iodine, should I add either only when I see they are moulting or on a regular basis? And if so, how much - the bottles are often designed for marine aquariums, corals etc, and not for brackish water and crabs.

Thanks again,

Sophie

 

[nmonks]

Calcium is rarely an issue with freshwater crabs or shrimps. Simply feeding them things like whole krill and unfilleted fish (lancefish for example) should provide all the calcium they need. For iodine, half the dose recommended for marine tanks appears to work well. You need to use it each week because the days leading up to moulting are actually the critical ones, so by the time you see moulting, it'll be too late.

Cheers, Neale

 

[sophiegackowski]

That's great, thanks so much. I've seen that they can live anywhere from around 2-4 years, maybe less, and so hope I can keep on top of everything and keep them happy! If there's any other tips or advice you have then feel free to post it, a newbie always needs a hand!