Power fractal blend:
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Painted shader blend:
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There's just a few different blending methods, all 'straight out of the box' caustics layer.(I removed the negative colour offset of the internal distribution fractal, just for better visibility in these demos).
The caustics layer simply gets added after the last shader you want it to appear over, usually, your last surface shader, like this:
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Any more problems, give's a shout. I don't have any difficulties in blending this shader at all.
Maybe if you tried to blend it by a smaller scale than the actual voronoi cells, or something, it might have difficulties but, I haven't found that. Hopefully, these make things clearer.