Peppermint shrimp dying

I have a problem: I bought a peppermint shrimp to eat aptasia in my 20 gallon and after a short acclimation it died after about 10 mins in my tank. I waited two days and got another this time I used a slow drip acclimation for over three hours. It was fine, exploring, and even ate a piece of aptasia I offered. However, after I added it to the tank it swam to the bottom and died as I watched. I have live rock, a small lawnmower blenny, four hermit crabs, two snails, an emerald crab, two clowns, and three BTA (all healthy and eating)... Any suggestions? I checked my water too and Ammonia is at 0, nitrate is low.

 

Sorry to hear that Do you have a quarantine tank? Could you tell us more about the acclimation?

 

I bought 2 also, they ate all of the Aptasia in my 125 gal tank. After they consumed all of them 3 days later they were no where to be found. I have some big Hermit crabs and a Emerald crab, maybe the shrimp were lunch.