Mystery clean up crew deaths!

[Jtempkin]

Mystery:

I have a 75 gallon tank with a variety of beginner corals (grasping , polyps, etc) and a couple clown fish. It has been running almost a year. I can not keep starfish/cucumbers/urchins alive! Water is all in normal parameters (double confirmed by the staff at Preuss pets in Lansing)

Already eliminated:
Copper- test at 0
Nitrite- under .25
Nitrates - under 5.
Ph/ammonia/kh- all good

What could be responsible for killing a clean up crew. Usually in under 2 weeks?

 

[sfin52]

Welcome to reef2reef. What are the tank inhabitants? Also are you hearing any noises in the tank like clicking or popping? How are you acclamating them?