  The flow of U(1) charge through dense fishnet diagrams, in a non-hermitian
matrix scalar field theory g_1Tr(\Sigma^\dagger\Sigma)^2 +
2g_1vTr\Sigma^{\dagger 2}\Sigma^2, is described by a 6-vertex model on a
``diamond'' lattice [1]. We give a direct calculation of the continuum
properties of the 6-vertex model on this novel lattice, explicitly confirming
the conclusions of [1], that, for 1/2 < v< \infty, they are identical to those
of a world-sheet scalar field compactified on a circle S_1. The radius of the
circle is related to the ratio v of quartic couplings by R^{-2} = 2T_0
arccos(1-1/2v^2). This direct computational approach may be of value in
generalizing the conclusions to the non-Abelian O(n) case.
