Hi Luke,
DISCLAIMER. I'm sure others have had good and bad experiences with these places. These are just my limited experiences and opinions. Hope this helps!
I think there are a lot of great places here! Like 95% of my fish purchases have been from online retailers like NY Aquatic and TSM Aquatics but I've purchased a couple from LFS. Here's my ratings in order.
#1 - Aquatek Tropical Fish - purchased a couple of fish from here. They stock fairly often so the quality and rareness of fish are decent. They have a lot of tanks so they have a wide variety. My +1 on this store is that they have variety and great quality reef food and a membership will give you a good discount that will way more than pay for itself over a year. It'll also get you a discount on most dry products and livestock.
#2 - River City Aquatics - this place gets #1 in my book for friendliness and experienced staff. When I bought my big tank, I called them asking if they did installs. I really just needed a few people to come to lift the thing. The owner offered to come when he closed up for the day and would bring a friend to help for only $25 each (of course I was going to pay them more than that). I ended up finding help and didn't need him to come but that was some customer service! I've also purchased many of my dry products, salt, etc from them. Every time I go in, they're doing water tests for another customer and giving recommendations on how to fix parameters. Always a good experience!
#3 - Austin Aqua Farms - purchased two Rainbow BTAs from them + a couple of hammers. They have some great quality anemones and corals, all reasonably priced. I didn't have the easiest buying experience during COVID since it was pull up and text when you arrive. Wait time was an hour one time and I was the only car there. Employee was having an off day and not too happy when I called again at 40 min wait asking what was going on. Nothing against livestock but was just part of my experience.
#4 - Gallery of Pets - saltwater is not their specialty, they do the full range of pets, however, they are all super friendly and always happy to help. One supplier online shipped me a large arrow crab that I did not want. Gallery of Pets happily took the crab off my hands, had it for a couple of weeks, and found it a new home.
#5 - Austin Aqua Dome - this place always seems busy! Employees are moving 100 mph and don't have much time to talk or answer questions. I talked to one lady a few times who was not knowledgeable. Did curbside for a whole bunch of macro and got a bag of random macro, none separated, and the one macro I ordered, they ended up not having. Also ordered a saltwater ph test kit and they gave me a freshwater one saying that was the only one they carried (can't use that). I'm sure they have people there who know their stuff, just my experience.