Id like to further reinforce the idea of scratching easily. Acrylic is a PAIN!!!! It really is! No matter how careful, youll put nasty scratches that will cause OCD people to go nuts!
Also, algae scrubbers such as mag-float will ruin the tank over time. Im talking THOUSANDS of micro scratches and whatnot. And yes, I am using the mag-floats made for acrylic.
Id go with aragonite sand as I beleive it is calcium carbonate, right? Thats going to be softer than silica sand by far. (Less likely to scratch the you know what out of the tank). Or at least, thats what I am guessing. No matter what, youll need to come up with a very strict habit when working near the tank.