I'm so bummed! All of my fish are dying!!!

[Kzang]

I would also inform the place (a LFS?) where you got the two tangs. They may have a latent infection that is kept at bay with non therapeutic level of copper (I hear it’s not uncommon), their next customers will be grateful to you.

This actually happened to me. They said they ran copper, but I didn't ask what level. In a day or two velvet sign of swimming into powerhead. A few days later even in copper, both PBT and blue tang dead.

 

[h2so4hurts]

Definitely velvet. Formalin bath for an hour and then get into a QT with chloroquine phosphate (spectrum sells this as a product called ich shield, it is not invert safe, treatment is 10 days in most cases). If you don't have a QT setup you can do pretty well with ammolock and 50% water changes every few days.

 

[mfollen]

Always plan for parasites on any new fish. It’s not the LFS’ responsibility.

 

[h2so4hurts]

Always plan for parasites on any new fish. It’s not the LFS’ responsibility.

While this is true, if an LFS routinely sells diseased fish that kill entire tanks then they're probably not going to be in business very long.