How to get over 100 users online mark!

Okay this has been bugging me for years!!!

For years now we've always had 100 or more users on the forum at any given moment in time. I've been waiting for quite some time as you know for this number to increase as I always see big forums increase in traffic visually. For example, forums that have the 100 or more users online at any given time typically increases over time to more such as 300 users online at any given time and then 500 and then 1000 and beyond.

Now for years I have been waiting for this to increase but for some reason it doesn't. Is there some special technique or strategy to accomplish these traffic spikes? I thought it was something that happened naturally and gradually yet for years the traffic is staying the same and I just don't understand. I see forums build up, go from 30 to 50 and then like mine where it's 100 or so users online at any given time and then I even see forums surpass mine like I said above and it goes from 100 to 300 to 500 and then 1000 and beyond at any given time.

What's the secret? :( There can't be anything blocking my site's traffic from expanding could there be? I have a firewall in place because of DDoS attacks and hacking attempts we've had last year.

I think there really could be something blocking my traffic because before we added the firewall and before we had so many problems with DDoS attacks and hackers etc, we were doing better. Like check this out: The most members online in one day was 1,535, 02-20-2009. What's going on? :(

Okay so here's an UPDATE.. So we've achieved over 100+ visitors continuously online [landmark], but the traffic just is NOT converting. Any ideas/suggestions why? We only achieve 15-30 user registrations per day. After analyzing our traffic, our traffic is all extremely targeted and organic coming from Google, and most of which do browse through quite a few pages of our site and does spend more than 2 minutes on our site. So what's the problem?

I run a big forum. As you said there is continuos grow on my stats. I can tell you forum grows because you add some increasing value to users. For example at the beginning no body believes you and choose you because you look small. As time passing each thread and topic you become stronger and people like big communities. You need to work harder untill that time. Because my niche is webmaster forum. I offer people a crowded webmaster marketplace.

Seo is a secret key for many forums. For example if you rank number 1 on forum search. People who look for a forum to discuss will drop yoursite. This will bring you power get the idea? You say 20-30 registrations. But is too small for growing. You need daily hundreds registrations. Most of the registrars are blind users. You grow only with very stable users. These people like to see your forum always online, fast, full of data and cool.

You eed to search in keyword tool and see what people may like to see on your forum. It depends on your niche. For example i rank number one on webmaster tools, webmaster forum, what's webmaster etc such related keywords and i offer useful content for webmasters. You can do too. I hope you got the idea.