Some of the local fish stores in the bay area sold tickets as well. I'm not sure if that's changed or not due to COVID.
The show itself is exactly like a farmer's market for produce - early bird gets the worm.
Vendors have booths with corals, fish, equipment. If you're staying there for awhile for the raffles, vendors are usually willing to hold your purchased livestock in their tank for you to pick up later when you leave.
With COVID, I'm not sure how it'll be. Pre-COVID-wise, it was fun, although it can get quite a bit crowded and hectic with the amount of hobbiest around looking for deals.