Almost all my fish died from fin rot

[Alec]

I recently started up in the fish hobby and I have had my freshwater talk for about 6ish months. All my fish have been healthy as well as the tank. I noticed a week or so ago some of the fish were hanging out near the top. l didn't notice anything else wrong with them and water parameters were fine.. First thing that came to mind was low oxygen, so I did a partial water change and added an airstone. Then here recently I noticed the fins all all my fish appeared to be damaged. I later found it to be most likely fin rot. I have no medicine on hand and unfortunately, I think its too far gone.

Anyway, if these other fish do end up dying or they survive and are well, is there anything I need to do to the tank to prepare it for new fish? 

[Yanni]

In the future, I would quarantine those fish to just make sure that they are healthy. I don't think you need to do anything to the tank, a water change would be good but other than that, you should be fine.