Hmmm, it's funny, 'cause my water sprite looks nothing like what you guys have..... and you both have the same thing. Maybe there's a third plant that is commonly called water sprite???
I've tried to convince some of my local mom-and-pop LFS to stop stocking non-aquatic plants but they just say that that's what the distributor sends them. Oh well.
Maxwell, your tank looks awesome, I really like the piece of driftwood you have. Are you sure that is Alternanthera sessilis? It looks alot like the A. reineckii that I have which is aquatic, although it does grow very slowly.
Keep up the good work, and keep the pictures coming!