HCA: Hermit Crab Association

I was thinking I could probably find a nice plastic tub to serve as a saltwater pool when I get my two new Strawberries. I could do that right? It wouldn't be fancy or anything, I'd just dig a cavity in the sand, and put the tub in, then fill it up with salt water? I wouldn't need some kind of pump to keep the water moving, would I? ( i have room for a pool could be a foot long, 5 inches wide, and 3 inches deep with gravel on the bottom and the old aquarium castle in the center. Ha, wouldn't that annoy the two residents there! )
Also, if I did that how often would I change the water?

It would work! I change my water weekly depending on how dirty it is. Just make sure you have some shells in the pool so small crabbies can climb out. and no you dont need a pump.