Today I'm starting my personal goal of redoing all of our fish tanks at the store. Due to neglect by the previous manager, I decided the best course of action would be to just redo them. The sponge filters in all the tanks cannot be replaced, as we can not simply afford to cycle all of the tanks from scratch. These sponges have been in there for close to a decade. I'm trying to think of the best plan, as it's quite hard. I want to rid any kind of disease that may be living in the tanks, so my first idea was to remove the gravel from each tank, put them into bleach water, followed by a thorough rise and soak in dechlorinator water (a cup of dechlor in a 5 gallon bucket of water). The same goes for any fake plants/decorations. What are your thoughts on acriflavine for getting rid of parasites that may still be inside tanks? We have a lot of it. Please feel free to throw some suggestions my way, it would be much appreciated.