Shrimp spasm/twitches question

[RebeccaPharmD]

Hello, I have recently registered with this forum, but have been a lurker for quite some time before that, trying to do some research on Red Cherry Shrimps. I started with a 10 gal tank, with Wood Shrimps and ghost shrimps with my betta to see if he would eat the ghost shrimp, or if I would be okay investing in a small colony of RCS. My betta left my ghost shrimps alone didn’t eat even just one- nor chase them when I watched him from a far-for several weeks, so I figured he’d be good with my RCS’s. However, I am going away starting pharmacy school in about a week here, and my school frowns upon having a tank larger then 3 gallons. So, I bought a 2.5 gallon, and decided to keep some cherry red shrimps along with my betta, with me while at school. I traded in my wood shrimp and ghost shrimps back to my LFS for some RCS’s, which I know I can easily keep in my smaller tank, since the wood shrimp get quite large.
My question is this; one of my shrimps has episodes it looks like spasms, twitches, or quite honestly, episodes of tourettes. I just cannot figure out what is wrong, as my other 6 or so shrimps are just fine and I have not seem them do this kind of behavior. My water parameters have been perfect with my cycled tank, as I was able to seed my 2.5 gallon off of my 10 gal. I have a Red Sea nano HOB filter, which is perfect for the 2.5 g tank that I am currently running. I have 0 amm, 0 nitrItes, and always >5 nitrAtes. I have pretty hard water, although I don’t know the exact level of hardness as I don’t have that type of tester. My pH is between 7.9 and 8.1, temp at a steady 76*F. I test my water parameters (amm, nitrite,nitrates) in my 2.5 gal every other day, as I know the levels in such a small tank can be thrown out of whack very easily. I have heavy ground cover, with a good amount of slow growing plants, java moss, java fern and java lace. I have a piece of driftwood that my shrimps seem to absolutely love to hide out in, as it is hollow. My substrate consists of smooth polished gravel which looks like river stones. I don’t use fertilizers. I have had SEVERAL molts. I used to use the Aquarium Pharmaceutical’s Stress Coat water conditioner, but after reading about how it gave some people’s shrimps problems with molting, I have switched to using Prime water conditioner. I have watched this shrimp that has the spastic episodes for quite some times, and SHE seems healthy overall. I have actually seen her molt just fine last week with no problems. I am just wondering if this shrimp has something else wrong with her. What she does it swims REALLY fast up to the top of the water, and just swims straight down even faster, throwing her self onto my substrate. I thought she died the first time I saw her do this. I sat there and watched her for probably 10 minutes not moving just laying on the bottom, and after seeing her not move, I went to get my net to fish her out of the tank, but just as the net touched her, she swam away like it was nothing. She doesn’t appear to be trying to jump out of the tank, and I don’t see why she would, as water parameters are just fine. I even have a nice healthy population of copepods swimming around in there. All of my other shrimps appear fine, all just relaxing in my moss and just walking around the bottom of my tank. She does this what I see probably once every day or two. If anyone has any idea as to what is happening with my one shrimp, or has any suggestions, I’d really appreciate it. Thank you!

Here are some photos:

[bulrush]

There have been rare cases where Prime has been a problem with inverts. Discontinue Prime and use another dechlor for 2 weeks and see if that clears things up. Also do a 30% water change when you get the new dechlor.

[RebeccaPharmD]

Wouldn't it affect my entire colony of shrimp, though? I'm also curious why other people have used prime sucessfully then with RCS's. I actually used Stress Coat before I got my shrimp, and read that the StressCoat gave problems with molting which is why I switched to the widley recommended prime.

[Mustafa]

The water conditioner is not really the issue here. I see a Betta swimming around in your shrimp tank. Even if the Betta does not outright eat the shrimp (it for sure will eat the babies though) its mere existence will stress out the shrimp. So the shrimp are always on the edge and ready to bolt. That may look like "spasms" but it's usually flight behavior. They're basically "running" for their lives every time they are disturbed.

[ShrimpFan]

I also think it may be a stress-related issue. I have observed this behavior in my 10-gallon shrimp-only tank--both my cherries and amanos have done this.

I noticed the spasms when I performed two very large water changes two days in a row. What happened was that I removed much of the water in the tank because I became concerned it was being polluted with tannins from some recently added driftwood. Then, the next day, my mother got a great deal on a table and wanted to replace the one I had my tank sitting on, so I had to empty most of the water again in order to move the tank to a new location. Furthermore, I made a huge mistake because I also replced the filter cartridge, thinking I might as well get everything "completely clean." Of course, this basically made it so my tank was no longer cycled. The shrimp became very stressed out as a result of the unavoidable second water change and of my stupidity in changing the filter cartidge. I suffered heavy losses and began to observe the "spasm" behavior in many of my shrimps. They now seem to have finally recovered, but it took them nearly two months to do so.

Perhaps your shrimp are acting this way because of being enclosed in a small space with a predatory fish, or because of some underlying water quality issue, etc.