You can do it--I totally believe it.
Really cool you want to open up a shot--and want some input!
Honestly, if you were in the US I'd want to shop at your store rather than those huge chains. aka talk to a real person who is willing to help me with my fishy needs+knows a lot :D
'If anyone has any ideas to throw out there (types of tanks, stands, selling live plants, or educational purposes, energy saving ideas aka electricity, water, etc) go ahead and post ^_^'
What do you mean by types of tanks? I don't know if what I'm about to say is at all going to be helpful but... xD I LOVE my fluval chi. Seriously it's so pretty and really a nice thing to have in my living room. Fred loves it too :D
I think it would be good to have a range of aesthetically pleasing tanks in a range of prices. Personally, I don't care much for those traditional tanks--sure, they do the job, but I'm all about the 'bling bling' xD personally. I like things to look nice. (not that traditional tanks don't look nice). Also, I really like glass tanks. Not a fan of plastic... And if you don't have something--order it! I think that's what I really appreciate from some places. If they don't have it, they will get it for me.
Personally, I like live plants better than the silk plants...they just seem to look nicer? Although I might get rid of my amazon sword for a silk plant

it's sort of high-maintenance compared to my anacharis and marimo. I also think it's a good thing to sell live plants that absorb a lot of ammonia. <-- that is a big perk for me when buying plants. Also, I think low maintenance plants would be best to sell. That way, you won't get 'oh my plant died.' D:
I would write up guides for each plant--light requirements, common names, ammonia absorption, etc. And always be willing to educate your customers on something--if you don't know, check. Instead of printing out little info sheets(waste of ink most of the time because they just toss it out), offer to email the file to them/post it on your website.
For education, I would start out by referring to your website or telling them in person, having some nice signs printed and laminated about the care of that particular fish.
For money saving, the best thing you can do is go digital. Sure--laptop is energy, but printer+ink+repairs+energy+etc. all that can add up.
I don't quite know how you could save money on water... Maybe you could use the fish water for the plants? (but plant water doesn't really need to be changed that often, right?)
Very excited for you--btw sorry if I repeated anything, didn't read through the thread.