Quote - yeah, my vote would be to make fishtank walls thick, e.g. 0.375 inch for 100-gallon tank.  there was issue with FFRender and transparency vs. refraction in re: shadows, but maybe they fixed it. 

If we're going for physical accuracy, then I agree.  However, unless the rest of the scene is also modelled to real world scale, and consistant, all that would do is extend render time for little to no visual gain.  Unless there's a bug with refraction as you suggest.

All objects should have some thickness for realistic results in physical render engines like Luxrender or Octane.  Often the appearance of depth can be faked, by creating just a "rim" of polys around a border edge, but when rendering in a physically accurate engine, it's best to create real geometry for it to calculate.

A fishtank doesn't need to be constructed of seperate slabs. You can build it as one single rectangular manifold object, and just add thickness to the object.  In most modelling applications, you can control the depth of the thickness in real world units as well.

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Tools :  3dsmax 2015, Daz Studio 4.6, PoserPro 2012, Blender v2.74

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