Good idea. I've been considering/wondering if I exposed it to controlled heat, say like with a heat gun, if I could kind of control the warpage and mold it into the shape I desire? Then I could add foam and maybe try the titebond method to make the foam look more natural on the edge/outside and add sand and rock to the bottom.
I have done this a couple of times and used GS to make the edges look more natural. You wont even have to heat it at all, jsut carve it to look good. I kept the lip on mine since most tupperware will warp. You can insert small, flat slate rocks to the almost dried GS along with small driftwood pieces to further its natural look.
I have an ultrasonic fogger and it will be devastating to any critter. The frequency is intense and the water is quite warm at the source of the vibrations. It takes some work to conceal them since most of them have a bright red light when turned on that radiates in every direction. They are mostly used inside fake waterfalls where they are completely hidden. I did a little DIY project to try and keep one in my newt build. I used a a 2" piece of PVC with a notch cut out for the cord. I kryloned it black and then hot glued a thick plastic screen over the top to keep the critters out. Also kryloned black. Trick is to only hot glue one edge so that you can lift up the screen like a flap to access the fogger. It worked well.
I hvae some of that weird screen left. I have no idea where to find it. It works perfect for this application and I hvae never seen it since. I found it in my classroom one day in the deep dark recesses of the science stock room. Who knows.........its probably 20 years old. I can easily put a piece in an envelope and send it to you if you want. Just pm me if your interested. good luck and keep us all posted!!