I'm not sure what you mean by "scary looking on the inside," but some of the best fish stores I have found are the ones that are not
neat and clean. I'm not talking about the fish tanks, but the store itself. These are the hole-in-the-wall stores that have been around for so long that they've accumulated stock with no room to put anything, anywhere. I usually find what I'm looking for in these types of stores, but it takes a collective effort to locate it.
I guess what I'm saying is, don't avoid the "scary on the inside" places. Bad neighborhoods...well that's another story.
Good luck on your search.