So sorry for your loss, I agree that water changes should be done at a different time than filter cleaning.
I don't have a bubbler. My filter circulates my water and that's how the majority of the oxyen gets to my fish. Plus I think with the stress of the water change, temperature change, and lack of filtration...you know.
Got an air pump yet?
I take it you don't get many power outages.
Have your Aro's eyes cleared up any?

same hereI'll keep my fingers crossed for your aro.
Good Luck.
Dr Joe
same hereI'll keep my fingers crossed for your aro.
Good Luck.
Dr Joe