I kind of suspect it might be trying to molt? Some of the other shrimp have molted today anyway.

The shrimp in question has been alternating between eating, and scratching awkwardly at its flanks/tail with its rear walking legs. Sometimes it'll start to bend a lot, and sometimes it'll bend and try to reach its tail (which it can't reach). It can get pretty frantic, before it gives up and goes back to picking for food.

It's the biggest least shy shrimp of the bunch I got, so other than this it doesn't appear to be under any kind of stress.

 

From what I have seen with my shrimp they could be cleaning themselves or they could be getting ready to molt, Now would be a perfect time to check your gH, kH and other parameters to make sure they're where they should be to help your little guys molt :) I also suggest that you consider adding some 'mineral balls' to ensure your shrimp have the required minerals to molt successfully. If you dont have any check out @newbreed's shop https://newbreedaquatics.com.au/.

Cheers
 

It's a relief to hear that it's nothing to be too alarmed about just yet.

My tank parameters are okish, I've been working on slowly lowering the GH, because it's somewhat high (10). The fish store where I got the shrimp is on the same water supply. 

I'm in the US, so I'm not sure I can do mineral balls, but I'll definitely look around and see what I can find that isn't suspicious looking. The rock I have in there is limestone, so I know at the very least that the shrimp won't be wanting for calcium carbonate.

Mineral balls can be purchased in the USA as well. I'm not entirely sure they are required if the water parameters are within check and the shrimp get a good diet.

If you want to lower the GH slowly over time, you probably want to remove that limestone...

To keep my hardnesses down I use RO water for top ups and water changes, Its basically mineral free and can be obtained relatively cheaply. I purchased a 3 stage RO+DI unit for $30 on a buy/sell/swap page that plugs directly into a garden hose, I fill a 25 L barrel and move it inside to the shrimp setup.
Then I compensate the lack of minerals with mineral balls to make sure the shrimp are just getting 'the good stuff'.
Like @Zoidburg said, the limestone wont help with the hardness and you may want to consider removing the limestone.
Either way you really need to bring that gH down, your shrimp may have issues molting unless you do.
 

The limestone hasn't been a problem for me so far, or rather it hasn't stopped me from lowering the GH from a 10 to a 7, and keeping it there, we'll see if it becomes more difficult to lower beyond that.

 

I don't want to take out the limestone because my local water has no buffering capacity to speak of, my tanks parameters stay relatively stable, but I still feel better knowing I have at least a little bit of kh rather than 0, and the limestone helps with that. It's honeycomb limestone (holey rock) so the softest parts are long gone.

 

edit: Also I've found a bunch of different sellers in the US, my main problem is knowing who is reputable, especially with something introducing secret trace elements. I think I've found a reputable seller, but it's definitely something I want to ruminate on first.

 

Edit edit: also been looking at RO units, but I seem to be doing fine passing some of my water through my water filter, it lowers the GH to a 2.

Edited September 6, 20169 yr by bluestarfish