Bradyrollie4, I have an old 360 gallon acrylic aquarium that I am replacing. It's 3/4" thick, and 6'x4'x2'. I'm replacing it because a couple of the seams looked iffy to me. No leaks or anything, just makes me a little nervous. I don't want to deal with the headache of reinforcing them so I can sleep at night, so I'm just replacing it. I'm confident the seams could be reinforced with some acrylic and weld-on, but again, I just don't want to deal with that, nor do I have time to deal with all that.
Anyway, I was thinking it might actually work well for your fish store. I'd recommend reinforcing the seams, but after that it would make a great display tank, or a backroom tank/sump. I'll give it to you for free if you want it. Let me know what you think!