Can Algae Wafers Kill Shrimp?

[Saltinthedesert]

About once a month I lose a group of Neocardina shrimp and have not been able to pinpoint the source down. At first I thought it was planaria and treated my tank which is now free of those worms but the deaths are still happening. KH, GH, nitrate, nitrate, ammonia etc. are all exactly where they are supposed to be. Temperature is high 70s. Weekly water changes of 20%  

I know that copper is super poisonous to shrimp and wondered if the copper in these wafers I feed the Pleco in that tank, which they always feast on, could be the cause. It’s pretty far down the ingredient list but I have to figure out the cause. Thoughts?

[KBOzzie59]

I actually feed those to my shrimp (cherry and blue velvet) and not had any problems.  Maybe a you got a bad batch?  Shrimp do need copper in their diet.  Even the Hikari Shrimp Cuisine has copper.

[Saltinthedesert]

I’ll add that the only roommates are a BN Pleco, a half dozen Chili Rasporas (juveniles) and a half dozen Norman Lampeyes (also juveniles). I’ve ever seen any of the fish peck at the shrimp but in desperation of an answer I’d put money on the pleco. 

[Saltinthedesert]

One more thought. The age of the shrimp that die have been consistent in each wave, but not consistent with each other across waves. This time around, it was all “teenagers” one phase before adulthood.