I've been having a slow die off of my shrimp lately in my 20g high tank lately and I've having a hard time figuring out why. Here are the details on the situation.
It's a very heavily planted naturally planted tank. It's been running for around 3 months now. It's been fully stocked for a while now with all the other inhabitants thriving so far. In started with the following:
5 peppered cories
7 threadfin rainbows
1 honey gourami
I am now down to around 6-10 shrimp, most likely towards the lower end of that number, but I didn't keep count when they died and it's hard to get a count with all the plants and hiding spaces. Other than plants I have 2 filters, 4 small stones (river stones purchased as aquarium ok) and a piece of mopani wood. I don't think any of the decorations are the issue as they were all there for a while before the problem started.
The deaths have been slow and occasional, one will die at a time and it could be days, even a week between deaths.
I just got a test kit for kh and gh today. Kh is at 0-3 degrees (0-50ppm) as it started turning yellow with the first drop. Gh is at 8-12 deg (140-200ppm) as it turned green on the 10th drop. I'm a little confused with kh and gh so I'm not sure if there are good or bad and what should be done to fix any issues.
The other issue I had that could have started this was that I started out with 4 peppered cories and one got an infection that I tried to treat with melafix and it seemed to screw with my cycle a bit as I had a bacterial bloom that turned into an green water algae issue. That is when I got the second filter which has an UV light. The water is now crystal clear. The deaths started before this issue although the majority of them after it. That was around three weeks ago.
I have dosed with Flourish Excel, but always at less than recommended amount. (never over 1ml which is the dosing amount for 10g) I stopped when it became apparent that deaths were an isolated incident.
With most of the deaths I just came in to find a dead body, sometimes whole, sometimes with a piece gone. (the dead bodies quickly become food) I don't think they are being killed by tankmates at all as the only once that possibly could is the Gourami and I've actually seen him getting pushed around by the shrimp before.
I did see a couple of the shrimp die. One was swimming in the water like he was trying to reach the top of the tank and was kind of moving in a circle in a way that almost looked like he was dancing. After some time he just fell to the bottom of the tank. He got up a few times only to fall right back down. The second one was similar but without the "dancing".
I want to build the numbers back up a bit, but I don't want to spend the money to get more shrimps until I know things are stable for them in the tank or else I'm just throwing money away. I'm sorry this was long, but any help that anyone can provide would be greatly appreciated.