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.
Appcleaner
Disk Doctor is developed in the UK and was awarded the 'Mac Gem’ award by MacWorld in 2013. CNET and other tech journalists also praise the functionality. It looks like a useful tool for Mac cleaning that removes junk slowing down and reducing the computing power of your Mac. May 18, 2017 Disk Cleaner does all the work for you! We’ve optimized the most efficient locations to quickly scan and remove all the junk taking up your valuable disk space. Stop wasting disk space on - Unneeded files leftover from uninstalled apps - Temporary internet files, - Old mail attachments,.
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.
For Safari and Flash, this check is more accurate
Apple Disk Cleaner
Disk Cleaner Mac Apps For Windows 7
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
Disk Space Cleaner
Over time, junk files, temporary files, all kinds of system files and other items you do not need at all accumulate on your Windows Computer. Those useless files take up valuable hard disk space and slow down your computer. Disk Space Cleaner can delete these unnecessary files on your hard disk to free up disk space and make your computer run faster. Disk Space Cleaner can scan and remove them within seconds, making it one of the most efficient disk cleaners out there.