I also don't QT my inverts. They are sensitive enough as it is. One slow drip acclimation is already enough to be deadly. The likelihood of parasites off of them, I read some article about it in my early years into the hobby, said that is under 1% due to it being so immeasurable due to the type that they would carry. I don't recall the reasons or all that goes into it all, but it stuck with me. And if it was provided by some of the experts from the forums here at the time like Mr X, then I took it as gospel.