A little off topic but...... Are you married?
The argument you described in the classic husband - wife disconnect:
- Men typically charge forward arguing only the facts, ignoring the pain, and using the facts to put the blame on the women (Problem was caused by high amonia, nitrates, whenever. As a fish keeper you should know that.)
- Women typically lead with the emotional outcome and want the man to acknowledge the pain first then accept the blame (I bought these fish from you and watched them die a horrible death; why didn't you tell me about the water before I brought them home to die)
Best thing to do in this case is what you did; stay out of it.
Emotion vs Fact
Venus vs Mars