I registered to chime in here, because I was excited to see another fishkeeper in the Bronx.
I highly recommend Zoo-Rama. They are much pricier than the chain stores, but they keep a lot more variety, cool oddballs like eels, hillstream loaches, fw shrimp, etc. They also have cool plants from time to time. The owner is very knowledgeable.
In general, if it's common, I'll go to the chains to save money, but for interesting stuff I go here.
2566 East Tremont Avenue
Bronx, NY 10461
(718) 430-0909