i asked that question when i took the kids to disneyland last month. i got this as a response.
"amazing aquariums and reefs is in orange that's the go to.
reef lounge is in anaheim, but both times i've been there i was underwhelmed. idk what their deal is, but like they didn't even have lights turned on for their tanks lol. i've heard they do a ton of importing and wholesale stuff for bigger places, but on the hobbyist level meh. they're opening a new store closer to me that i'm going to check out next weekend so maybe i'll be whelmed
2gc and calikid aren't super far, but i've never been to either one. calikid i've heard is really sketch on whether or not they'll be open
vivid is way up north by burbank. unique is there too, but unique is moving and/or closed to the public
harry's marine life in gardena is a wholesale that's open to the public, but it's far from where you'll be. and kinda hood. they do bring in reefraft stuff tho"
for me, amazing aquariums was a nice shop. vivid didnt have much sps when i went there or else id walk out with a vivid's insanity.