I'd advise you to setup shop in your basement first, and learn how to maintan, 50 aquariums, all that is learned there can be transfered to the business.
First of all, decide where your fish are coming from. There are 3 wholesalers, 2 in washington, 1 in oregon. Then there is out of state, which means you'll want to be located near seatac.
Also, 50% of your sales will be guppies, tetras etc. Don't get me wrong, you'll have lots of cichlid patrons as well. However you will net more profet from common fish than the cichlid die hards.
Next I advise you to not carry many dry goods. As wholesale prices vs internet pricing is difficult at best. Your competitors are dr fosters, big als etc. Get wholesale price list, then compare it to online, and realize they're oporating without a storefront overhead, and run at only a %20 markup over list cost.
A local fish store should focus on what is rather bought in person than online. Fish, tanks, emergency meds etc. Food, lighting, filters, etc, will be bought online for the most part, still have some of those on hand, cause some people will want to support you. However people also like to save their dollars where they can.
In my experience, the most important thing to a store is, fish health, and fish knowledge. People are willing to pay extra for a fish that is healthy, and someone who can advise them and help them from making a mistake when setting up a tank.
Pick your niche and stay with it, don't be a jack of all trades. You'll just get down rated by customers. You'll have to staff an expert saltwater person every hour you're open, or you'll get a rep as bad as petco for advise etc. Same thing goes for your cichlids, you can't have someone who can keep fish, but can't show the difference between your victorian cichlids. Anyone can show some people peacocks, mbunas etc. Victorians make employees head spin, and honestly they probably don't care enough to learn them.
Don't focus on being the cheapest price, there is always someone out there that will undercut you. Focus on offering the best knowledge. Time is money, if you can provide someone with correct knowledge the first time, they will value that, over saving $2 on a fish, but having compatibility problems.
There are many aspects to this business, that you've never realized will come into play, until you've been in the business. For instance, finding a tax accountant, that specializes in livestock, so that you can claim your losses on your taxes etc.
As for aquariums as the storefront. The reason it isnt done, is it makes it much harder to control your store temperature. Not to mention those display tank's temperature. On days like today, you'd be losing fish, or having your roll doors down. Giving the impression you're closed. In Washington, you don't need to glitz and glam of the north east where good fish shops are a dime a dozen, all you need is a honest trade, with knowledge to back it.