I have a feeling the sub line isn't quite suggestive enough..."silver surfer" might still attracted...well you know...
But a couple things...
1. Block buttons are really effective. By hiding content from users you find inappropriate, it is easier to just enjoy your part of the space.
2. Ignoring inappropriate people is soooooo much more powerful than telling them to "bugger off". All attention is positive attention (even attention that was intended to be negative)
3. Discussing openly about "how nice it is to talk about gardening" also helps people take a hint.
I'm finding rooms go through phases...don't worry...it will get good again

Be part of the positive change.
Also...perhaps a "break room" for people who want to get away from all the adult stuff... might be a thing (rather than a tacobar or rainbow lounge)