Problem in Established Tank

[jeremy3721]

I have had my tank setup for a year now with no new additions. Queen Angel, Red Coris Wrasse, Maroon Clown, Fu Manchu Lion, and Purple Tang.

I decided to add a sand sifter to help keep the tank a little cleaner underneith the live rock. I quarantined the sand sifter for almost 3 weeks and added him to the tank 4 days ago.

It looked like he was being skittish yesterday and today he is dead and my Queen Angel is breathing rapidly from his left gill. He is cowarding under the rocks now and I'm very upset with myself for attempting to add a new fish.

Does anyone know what the problem could be. All water perameters are perfect.

 

[talenzmeier]

Water Change

Obviously the sand sifter was carrying some kind of microrganism that killed it and has infected at least the Tang. I'd quarantine the Tang and medicate it and I'd do a 25% water change. Have there been flucuations in temperature and is everything ok with the live rock?