Disinfecting aquarium/decor/equipment after disease?

What type if disease was it? Typically most diseases are a result of stress and a lowered immune system and sterilizing a tank isn't needed. Finding the cause of stress would more so be needed and treating, for example. The fish could catch a disease from lowered, fluctuating temperatures. Your solution would be to purchase a heater, and if ou already do have one, then you should get a more so better one

Such diseases that a tank encounters, and it doesn't have to be sterilized

-Fungal diseases

-Ich

-Dropsy

-swim bladder disease

-fin rot

-tail biting