Alfredshouse is gone.....

[Nate]

I would be willing to place a large bet on low oxygen levels. Buildup of protein on the surface...usually happens when someone is not using a sump, and an inadequate hang on skimmer (i dont know what skimmer you have/had), and little to no powerheads pointed up at the surface. Did you have a slimy coating on the surface of your aquarium?

Nate

However this is not caused directly by the adding of fish, it would happen eventually if you just had 1 fish. But the adding of new fish increased your need for available oxygen, with that, the new fish are stressed and their oxygen uptake is thus increased, and in the end it comes to a point where no one can breathe and they die. Good thing is your corals should be fine, I have seen them handle this no problem

[my2rotties]

I'm so sorry about your losses. This really sucks to hear about it. However you will learn from it, and be a better hobbyist after the shock is over. I agree with the posts about oxygen starvation and would look into that. When I first started out I inherited a tank with fish when I bought this house. It had a Ehiem filter and it stopped pumping one night and killed most of my fish. We still have no clue why it shut down since it was clean inside.

So sorry about Alfred.

[dkcrx]

What kind of skimmer? and most important, did you spray or use any chemical cleaners in your home? even smoke? theskimmer can inject the residuals from the air into your water cusing just what you have experienced including your PH drop. And at 7.6 that alone can kill off everything.