Very sorry for your loss. But you're absolutely right, he was probably unhealthy when you got him. You took great care of him until the end. If he seemed content with you, he must've been happy right up until he died.

I do again want to thank you though for taking in a frog that was in need of a good home, sick or deformed or whatever. It takes a lot of a person to do something good like that, and I give you big props.

As for sanitizing the tank, a bunch of warm water and cupful of bleach should do well. Also, you can use frog-safe antibacterial cleanser, I use Zoo Med's Wipe Out! to clean my tanks.

I wish you better luck in your other frog endeavors!