SSSF are a no-no because they typically starve in the home aquarium. Once they deplete the sand of nutrients it is all down hill. You probably won't see them at all until they are starting to go hungry and by then they will likely starve to death.
As far as oxygen levels I think you'd find your pH hard to maintain high enough if you were having an O2
problem, but other than that indicator, I'm not sure. You'd need a meter, I guess.
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