Warning this thing is toxic

We bought about 6 weeks before these Aquarium Deco also due to the positive review of my Vorrezensenten and put it in our shrimp aquarium (32 liters). After about a week, all shrimp were dead and we thought we had made a mistake with any of the food or the water chemistry. (But before that we had three months no problems with our healthy and lively shrimp had ... funny thing ...).
Two weeks later we realized this thing in our second aquarium (60 liters) with two fish. After about a week, the fish were so strangely lethargic, tired, swam little and slowly, ate little fish food lay. They were obviously ill and we did not know what's going on. We performed a complete water exchange (60 liters) and then we forgot to use this decorative thing again.
Then we realized with surprise that the fish in less than two days were kicking back, swam back and forth fast and ate normally again. What was going on here only?
All of this is two weeks since, the fish have since permanently alert and healthy, and we became subsequently clear what happened here: This thing has poisoned our shrimp and it almost would have killed our fish.
Hands off.
PS if you have experienced this review helpful: I am very pleased with each click on the "Yes" button - it's nice when you realize that it is useful to create a review here.