/cgl/ - Cosplay & EGL

So I'm trying to make pic related.
Currently in the planning phase and am drawing out measurements and deciding on materials.
I can figure out how to make every part of this except for the big fucking tank and metal frame that holds it in place.
What if I buy a huge fucking block of styrofoam and carved it into the shape of the tank, smoothed it out, covered it in some sorta sealant or some other coating, and painted it chrome
Or should I use something that isn't styrofoam?

So I'm trying to make pic related.
Currently in the planning phase and am drawing out measurements and deciding on materials.
I can figure out how to make every part of this except for the big fucking tank and metal frame that holds it in place.
Can anybody offer any help here? I don't even know what I'd make the tank out of.