Think of lettuce, brocolli, etc. as potato chips for tangs
Now, I've read exactly opposite that on this forum also. Many articles support feeding with many types of vegetables. Like the thread from when Qsharks purple tang died. I can't find it now to reference it.
Anyway the owner at my LFS
simply states that if it isn't in the ocean it is not good for fish.
Of course she believes in bio-balls and leaving carbon in the tank for VERY long times.
She did give me some disc shaped Spirulina. I usually feed it in flake form. It sticks on the side of the glass and small chunks fall off of it.
Tang always eats the flakes and likes the chunks falling off, but does it contribute to poor water quality if he doesn't eat it all.
How do you guys keep the dried seaweed from getting dumped down the overflow. My tang rips it out of the clip in about 22 seconds, and then it free floats until it goes over the edge.