Can't recreate particles/additive shader

I have a caustic texture (from Liquid Effect V1 in the asset store) on the undersurface of a body of water, and I'm using the standard particles/additive shader on it. I need to modify the intensity of the caustic, but there's no alpha channel on the shader. So I tried to recreate the particles/additive shader in ShaderForge, but when I try to render in my build, the caustics do not appear, no matter what I do with the shader and its properties. I've attempted all the combinations of textures available vs. type shader in ShaderForge, but can't seem to get the caustic to render. Any ideas?

Thanks