Okay, here is my issue:
I received a larger tank from a friend of mine a few weeks ago. It's a 2.5 gallon. I bought 2 guppies for it from a local pet store, but they ended up with fungus. They had cottony white patches on them and died a few days later. I was treating them for the fungus, but they ended up dying anyways.

I also had a few live plants in the tank with the fungus fish.
Well, now, I want to move my Betta, Vegas, from his tiny one gallon to the new (clean) 2.5 gallon, but I want to put the live plants in. I'm SO VERY worried that the plants and some of the decor got contaminated. I REALLY don't want to infect Vegas, but he really needs a bigger tank.
How do I make SURE that EVERYTHING is clean enough for my betta? The gravel, the plants, the decor, everything? I'm getting a new air stone and new filtration for him. He is my only betta, and want to make sure he stays happy and healthy!
Thanks everyone!!