Here we go again: MIs, Take III

[George]

I think (angel) fish dead overnight has some reasons other than oxygen. For a couple year, I ran a tank that has no skimmer. The tank had some very sensitive angelfish like golden and regal among other angelfish. All fish looked healthy and happy. As a matter of fact, one night I forgot to turn on my power heads after a maintenance. All fish were ok the next day morning.
I since upgraded that tank to a bigger one with a skimmer. But I am not hesitate to run a angelfish tank without a skimmer again. The only reason I wanted a skimmer in that tank was because I wanted to keep the water clean in order to keep some corals.