I want to put a mushroom in their terrarium

[Tree frog maniac]

This is from 1975 from a tree here in Canada my grandfather took it off a tree! This meant it's over 30 years old! Do u think it's old enough to kill off any bugs that were in it so I could put it with my dumpys or my milks! Not sure yet.

[Tongue Flicker]

It could still catch molds if kept too moist since it a petrified organic material now

[Louis Charles Bruckner]

I actually would use it to cast a mold and make a plaster replica and paint and seal it.
Use some plastic coated magnets to mount it anywhere you want and be able to move it for cleaning.

[Silkmoth]

Im afraid it will rot from the warmth and humidity. I think the casting a mold idea is a good one. Its a handsome bracket fungi.