Nice set up. I like it a lot. I had a RES as a kid, was a great pet. Currently, I have a leopard tortoise, much less messy than the water variety... I love water turtles, but Don't particularly want the work.
Actually, the size law is a federal law passed in the 70's to prevent spread of salmonella. No turtle or tortoise under four inches in size may be sold other than for educational purposes. (o.k., my Hermes was under 4", but he did visit my math classroom, and it's not illegal to buy them, just to sell them at that size). This law came about when there were tons of RES (and other turtles) in tiny bowls in dime stores, and they were tiny. There were tons of salmonella concerns about it (water turtles are worse than tortoises cause they poo in the water and spread the salmonella around more, but all reptiles carry some salmonella risk, just like all cows and people have e-coli in their guts). I wish the law had been passed for the sake of the turtles (tiny turtles living six months in a bowl only to die a horrid death is not good).
I usually only carry tortoises or mostly land turtles at my store. I don't like the mess of the water turtles, and no one wants to house them properly--20 long tanks, no lighting etc. SIGH. I also get tons of people wanting dime sized or quarter sized turtles. I explain the law and they are pissed. they say I had a turtle that lived six months as a kid, it did great. Uh huh, try sixty years for a life span....
There are many tourist traps and other places that sell small turtles, but they are usually shut down fairly quickly. I call the authorities on any I find out about around here... it's just a horrid predicament for the turtles, even if the law is only about salmonella, if it can save a few turtles, all the better.
now, someone recently came in and bought a huge 75g set up for her turtle, and all the works, and a great big cannister filter and tons of great lighting. Basically asked me to go through with her, and recommend the best of the best products for her turtle. That was awesome. Not only did I make a great sale, but I also knew an animal was being well cared for. Those kinds of customers make me really happy!