The problem I see with hobby groups is that hobbies attract a broad spectrum of people who otherwise normally wouldn't associate. It takes strong leadership, activities, meeting places, and agendas that are aggressively inclusive, and avoid things that would be a wedge.
Leadership is obviously going to whomever takes the reigns and does it.
Activities would be things like fragging demos, back stage tours of the city aquarium, tank builds, swap meets.... and every meeting has to include something like that.
Meeting time is also import. Most people have jobs, and most people who have jobs work during the day - but it's not safe to assume that most people work a 9-5 M-F job. Just by looking at successful groups that meet for a variety of reasons the times that seem to work well are mid-week evenings and Sunday post-Church hours.
Meeting place(s) are HUGE. Too many hobby groups meet at churches and bars, both are places that are by their very nature exclusive regardless of membership dues. I would propose that whomever is serious about leading a group contact the city Aquarium and see if, as a group, they could facilitate us once a month or something.... I would gladly pay dues to a club if it included a discounted annual pass to the aquarium. Right now a "Ranger Club" member ship is $150 for 5 people per year and includes the zoo and biopark as well as the Aquarium. I suspect the city would be open to discussion of further discounts for a larger group should one form, and perhaps allow more "one time guest" passes for specific meeting days to encourage new members to join.
Meetings held at members houses don't appeal to everyone. I know I am often uncomfortable in a strangers house, even if I've known them informally via the Internet for years. A more public meeting place is much more inclusive, and as naturally happens in clubs friendships will form, and people will gravitate towards other members residences and tanks as an organic process. I love to show off my tank and get feedback on it, but if it were in my house I wouldn't really want to just invite the public in to show off my tank.
Anyways, that's my 2¢... would love to get involved, but would also like to see something form even if I can't be a part right now.