thanks again for your help.
I did set up a new tank and transfered a part of the shrimp there. So far, they are "fine". I will watch them.
I also did a big water change in the old tank, since I don't know, which option is better. In the old tank is still the active carbon. I also lifted all the rocks and looked under the gravel to remove dead shrimp.
Since I do not know, if paint is the real reason or maybe dying algae due to the rearrangement of the lava rocks, or maybe feeding too much, it's all guessing.
I did set up a new tank and transfered a part of the shrimp there. So far, they are "fine". I will watch them.
I also did a big water change in the old tank, since I don't know, which option is better. In the old tank is still the active carbon. I also lifted all the rocks and looked under the gravel to remove dead shrimp.
Since I do not know, if paint is the real reason or maybe dying algae due to the rearrangement of the lava rocks, or maybe feeding too much, it's all guessing.