According to the nutritional data supplied to me by the US distributor of New Era (Living Color) (via the manufacturer) the New Era grazing log contains Ascophylum, Ulva and Dulce algae, but here's how things play out on the actual ingredient list.
Grazing Log Diet
Composition
Low temp fish meal
Shrimp
Squid
Fibre
Starch
Vitamin pre mix
Mussel
Mineral pre mix
Blended fish oil
Blended algae
Which appears to be almost identical to the composition of their algae pellets.
Algae Pellets
Composition
Low temp fish meal
Shrimp
Squid
Fibre
Starch
Mussel
Vitamin pre mix
Mineral pre mix
Blended fish oil
Blended Algae
I don't think that I need to point out the obvious .......
naesco ........ if sinking discs with a high inclusion rate of aquatic plant matter is what you are after, have you considered these?
http://www.omegasea.net/veggie_rounds.html
Having never used them I can't vouch for anything beyond what you see on the label, but nutrient wise they certainly appear to be far better suited to tangs, than the Wardley discs. Main ingredients are Kelp & Spirulina, and they are not loaded with cheap terrestrial based plant matter. (no corn, no canola, no rice, no soy, no linseed, no barley, etc)
HTH