I introduced 20 Amano shrimp to my tank with manado and within 4 hours I noticed a dead shrimp, on further inspection about 8 dead bodies and the rest very sick looking, I removed them into another tank with just black fine sand and ended up with most of the sick ones dying over the next few hours. I have just 5 survivors that seem to be OK after 48 hours of not moving too much. I also noticed that tiny bits of the substrate sticks to my magnetic glass cleaner, it looks to have metal filing or something metallic in it. Most likely this is what killed all the shrimp, at least they were the cheap ones!!!!