There is a place in Elmsford NY, Rt 119 near the Saw Mill. Although I haven't been there in quite some time. The owner had a blue ring octopus in a bag "acclimating", and I overheard him talking to a customer saying "no, not all blue rings are deadly...only the ones from Australia". I immediately walked out and never looked back.
There is Wet & Wild in Peekskill NY, but his stock has been minimal of late. I don't know if he's restocked. Haven't been there in a while either.
In Stamford CT there is Reef & Fin. Excellent store, but extremely pricey. If you can talk them down on an item, you can come home with a nice coral or fish. My personal preference.
House of Fins in Greenwich CT, also extremely pricey, and the help are a bunch of snobs who treat you as if you're an idiot. I never shop here.