One way to filter adult content is to use opendns nameservers. I think OpenDNS filters out adult content out by default. What you do is change the dns settings on your router to point to the OpenDNS ones. Here are instructions on how to do this from the OpenDNS website:
Open the preferences for your router.
Often, the preferences are set in your web browser, via a URL with numbers (example: http://192.168.0.1). You may need a password.
If you're like us, and you set the router password long ago and cannot remember it now, you can often reset the password to the manufacturer default by pressing a button on the router itself.
Or preferences may be set via specific application for your router, which you installed on your computer when you added the router.
Find the DNS server settings.
Scan for the letters DNS next to a field which allows two or three sets of numbers, each broken into four groups of one to three numbers.
Put in the OpenDNS server addresses, 184.108.40.206 and 220.127.116.11, as your DNS server settings and save/apply.
If that doesn't work, you may have to create a free account on the OpenDNS website and create the filters from there.
More info here: https://www.opendns.com/setupguide/#familyshield