Dude,

First, your tank looks awesome.

Second, not much advice but wanted to show you my conundrum.

My frag tank (aka, Milly's tank) is tied to my tank. Both share a common sump. The frag tank has green algae growing all over. Mine... Not a trace. I actually pull off tufts of the algae and put the rock into my tank. Within a few days the rock is completely denuded.

The only difference is my tank has a yellow tang (that I want out) and a yellow rim tang that grazes the algae.

The frag tank only has a hippo which IMO isn't a very good grazer.

You could try hydrogen.