Fish are dying

[Goldenpuffer11]

Need help ASAP!!! I have a 200g saltwater tank.
Fish in tank:
Gold heart trigger 6inches
Golden puffer 12inches
2 passer angelfish 7inches
Emperor 8inches
Maculosus angelfish 12 inches
Red Sea sail fin 6 inches
Pasonifer 7 inches

Fish that just died:
Blue ring angel 12inches
Achilles tang 7inches
Scribble angel 8 inches

I have praziproed the tank, did water changes, coppered the tank, fresh water dipped my fish and still cant find out what is killing my fish. Fish are breathing heavy, white lesions on my golden puffer and dead blue ring angel. I need help before i lose all of them!

 

[Deinonych]

When was the last fish added? Was it quarantined? If so, treatment protocol?

 

[mattcoug]

If pratzi and copper did nothing, sounds like you are looking at brooklynella. Better get some formalin asap. If you have a microscope handy you can make a definitive diagnosis.

 

[Goldenpuffer11]

I have not added any new fish in a long time. I have transferred fish from my 300g over but nothing new. I have also treated my tank with formaldehyde and nothing is working. Should i do formaldehyde again.