Mac's don't need defragging as OS X automatically writes 2Gb or below sized files to one contiguous space on the drive. There are certain cases where's it's needed to free up a large spaces on the drive, but not something everyone has to do.
Clean My Mac 3 Reviews
Far as other Mac maintainence, there really isn't any except to backup one's files regularly. Keeping Software Updated and run a web browser check to make sure the plug-ins are current.
Mar 08, 2017 No.4 Free Mac cleaner: OmniDiskSweeper - Free hard drive cleaner. OmniDiskSweeper is one free Mac cleaner to find and delete big files that taking up hard drive space and also it can help you recover lost disk space. OmniDiskSweeper helps you sort every file on your Mac by size and you can identify the biggest file to delete it. The Top 10 Best Free Antivirus & Cleaner for Mac 2019. But you are currently running an online system with no free Malware proteciton, you have Malware. Oct 07, 2019 How to free up storage space on your Mac Save space by storing your content in iCloud or using built-in tools to find and remove large or unneeded files. Optimized Storage in macOS Sierra and later. can save space by storing your content in iCloud and making it available on demand.
Free Mac System Cleaner Software
For Safari and Flash, this check is more accurate
Most of those cleaning programs are junk, especially MacKeeper.
If your friend got onto your computer and visited a bunch of adult sites, then I would recommend something like OnyX, doing ALL the cleaning and maintenance aspects and rebooting, perhaps followed by a Disk Utility Erase free space.
CCleaner beta is out for OS X, used on PC's and combines cleaning and scrubbing of the drive if setup correctly.
If your interested in performance, read my post here