Since I was in San Pedro for Dreamstate Harbor, I had a couple of hours on the 2nd day to visit the aquarium before the festival started at 15:00, which was just enough. We ran out of time the previous day to visit it while going around San Pedro with Thomas
It's not a huge aquarium, it's actually been a teaching aquarium for many years, and sure enough it had lots of explanations on lots of things, which allowed me to pass the 2 hours even if the displays were more on the limited side. It's not a destination aquarium, especially with Long Beach Aquarium nearby, but I enjoyed my time there.
The rest of San Pedro is here