[Axiose]

I have a nano tank that's been inhabited by a variety of dwarf shrimp for quite some time. My pride is the small population of sss crs that are dying as we speak. My tank has a large piece of matured driftwood that's covered in a Java moss carpet I've been working on. I did a 40-50% water change as I normally preform on a weekly basis using RO. I was previously using a mixture with tap to add minerals, but today I intended to add in a piece of shirakura mineral stone I decided to try out (due to a lack of substantial info). After doing the change I added the rock and almost immediately I got an intense reaction from one of the crs in the tank. It began violently flipping around and lost control of its bodily functions. It then spread shortly after to two orange pumpkins. They're spasms seem to result in eventual paralysis. As I'm writing this post none have died yet but it looks very grim for them. I pulled the mineral rock out almost immediately after noticing a reaction (was less than 100mg). I've performed two water changes (to hopefully dilute the problem) and tested all my parameters.

Ph 6.4 ammonia 0 nitrite 0 nitrate 0 gh 1 kh 1

Basically inquiring as to any thoughts or experience anyone has on the subject. All other forums I've come across seem unhelpful.

 

[Axiose]

Yes I understand, it's been a steady decline in hardness due to the absence of tap water in the last couple water changes and I intended for these rocks to correct it. As I understand it, the hardness should not have any immediate or lethal reaction to the shrimp so long as it's not an extreme or immediate change. I'm not an expert, but it appears to only affect moulting over time. Nearly 12 hours has passed since the incident and things seem to have mellowed out in the tank. No more spasms and the death toll topped out at 4 with two crs and two orange. While some appear to be normal, others do still seem to be perhaps a bit lethargic or just inactive.