Fish Forum Critique - and why google hammered me?

[myfishtanknet]

Hello,

I have a forum that has been running for about 8 years now. over 11,000 members and close to being a big board status. yay!

earlier in the month i got hammered by google and lost pretty much all traffic for some reason.

an old thread about my site is here:
Losing Indexed Pages quickly..but not worried..yet. - vBulletin SEO Forums

I haven't really done anything different to the site so i'm not sure what's going on.

oh yea..giving you my forum would help.

Online Freshwater and Saltwater Fish Community - In Depth Fish Reviews of Fish, Plants, Corals and other Aquatic Species

So if anyone can help..

1. any vbSEO tweaks and tips
2. any reasons why google hates me now
3. and any other good ways of monetizing.

Thanks!

[AliMH]

these days i have the same experience and drop from 30k page to 15k indexed page, first i think my changes in templates (using image alt tags and other stuffs) cause to this losing.
what is going on?