Reclaim unused space on thin provisioned disk?

Hi all.

I have ESXi host with 300GB space, and 5 Linux guests. All of them have been configured to use thin provisioned disk, and to use max 200GB.

First guest used about 100GB. So I tried to remove temp and some large files. Although I removed around 30GB from it, ESXi still shows that it is using 100GB.

A read on the forum that it isn't possible to reclaim this freed space without VMotion and moving this VM to another datastore.

Is this really true? Is there any tool or procedure to reclaim unused space without downtime?