Thanks for setting up the community!

Unfortunately, I won’t be able to be of any help with moderation. However, there are some ideas I would like to share, up to you in the community to decide whether or not they are any good. In my opinion, a community like this can flourish if there is a good mix of serious and lighthearted stuff going on. A few ideas on how to get this: 

Meme monday: memes of all kinds relating to science fiction welcome, except Star Wars. Not hating on star wars memes, but there are maybe dozens of communities dedicated to those.

Guess it Wednesday:  stills from a movie or TV show, the rest of us try to guess which one. Of course bonus for season and episode guess as well. May also feature short excerpts from books to be guest.

Caption competition friday/wrong amswers only: one of the moderators posts and image from a work of Science Fiction, the rest of us try to make a funny caption. Alternatively, the moderator asks a question about the image, and we are only allowed to give wrong answers.

It might be good to also discuss the duration of [spoilers] tag on a post after release of certain material

I’m only partly serious about this one, but maybe hating on cowboy bebop should lead to an immediate ban.

Hey, I could help you out. I'm a mod on MarvelStudios and Movies currently and I do the weekly tv and movie discussion threads. I could do the same here for current airing series as well as integrate some of the ideas below. I'm also currently revamping our sidebars to be more community specific as well.

A successful social media community is largely dependent on discussion and the proliferation of memes, but Science Fiction is a pretty broad subject matter. You could try to increase engagement by narrowing it down a bit. For example, you could pin a weekly or daily discussion about the latest Sci Fi news and media or create a 'book of the month' club to help focus discussion.