In the last 2 days I have noticed my red cherry shrimp acting a little strangely - standing still around the tank. When they are active they seem totally normal - busy picking little bits off the plants, swimming around, very enthusiastic about being fed!
I did a little research and found a few possible causes, but I wanted to post here to see if anybody can spot something I've missed or think of anything else I should check for.
It's a 10 gallon tank that was set up December of 2018 and houses only red cherry shrimp and a single small nerite. The only addition was 10 new cherries purchased from someone on here to add genetic diversity - they were added in either March or May of this year and had absolutely no issues. I use treated tap water with Salty Shrimp GH/KH+ and RO to top off. Temperature was running 23 C for most of the tank's life; I removed the heater 2 days ago when I realised it was mid summer and actually heating the water! The tank now runs around 22.5 degrees (it's hot here!).
Here's the 4 possible causes I found and my thoughts on each -
1) Low dissolved oxygen
I think this is unlikely as nothing in the system has changed, except slightly lower temps which should hold more oxygen. I have 2 sponge filters and I feel my surface agitation is good; there is minimal bacterial film or scum on the surface. The tank is half open at the top too so should have good circulation.
2) Bacterial infection
Again I think unlikely as I have not had any deaths (unless they were very sneaky about it). From what I can see nobody looks cloudy, although they mostly have good red colour and so their shells are pretty opaque.
3) GH/KH in a bad range
I tested these tonight and got GH 5, KH 3. This is I think a good value for cherry shrimp, and is where I've been aiming to keep my numbers as long as I have had them. This one is more of a contender though since I am a bit lax about testing here - I rely on mixing the same amount of shrimp mineral each time and keeping track of water change water vs RO top off amounts.
Additionally, I've fallen a bit behind on their maintenance recently and let the tank run at a lower water level than it should be, but that's been true for a few months now with no noticeable issues. I did a 10% water change 2 days ago and with that, I did bring the tank back up to its correct level - so I suppose this could have caused a shift in the GH and maybe upset them? I'm not sure though since I used a drip acclimation line to refill the tank so the addition of the top off water took over 24 hours, which I think should be enough to allow for a slow adjustment. Also, any shift would have been from higher GH to lower, which I believe is supposed to be easier on the animal.
4) Iodine deficiency
This could be it, if I rule out all the other options. I'm going to be taking a sample of my water to my LFS tomorrow to run their tests on it, and if all comes up clear there, I'll get a small bottle of Seachem Reef Iodide to supplement with.
Other than the standing still, everyone seems healthy and happy enough, so I don't think it's anything too severe! Thanks in advance for any help or insights you might have