heading says it all really. windows 10, have recently uninstalled and reinstalled. MS support said to leavve f-secure off...
Ultralight aquarius installer most likely about "daily" on-the-fly updates for Aquarius-database (advanced signature-based engine); It should be only temporary (one minute -- three minutes; or so);
Does your experience about "stable" disk-usage (hours or so)?
When fresh "database's updates" released by F-Secure -> your installation able to download it and then 'install' it (for using under F-Secure software);
It can be with "double" backup for previous state of databases. And "write/copy/unpack/extract/deploy" fresh ones. Maybe "such" drive usage can be expected. Because -> I always feel when Aquarius-updates are installing. But not sure about your certain situation OR what if it can be improved.
Maybe you able to contact F-Secure Support Channels (chat/phone) directly:
For proper investigation - does installing daily on-the-fly updates for Aquarius core should be with this view (as your experience);