Hello I have an issue for which I cannot the answer. I've had caridinas for a few years now, but recently built a new tank (116l) with lots of moss, tech soil (shrimp king from dennerle), roots, stones ... but unexplained deaths. Tank has been running since mid february and since then I have done weekly water changes (around 10%) I have an external filter (Eheim classic 150) & also a sponge filter with air sent in the tank for oxygen. My parameters are: PH = 6.4 GH =