Believe it or not, one of the least useable proteins for carp, unless as @emmcee says, you add an additional enzyme. (Bengers anyone?)
Personally I think that as carp are omnivorous, able to eat both vegetable and meat matter (within constraints), a meat or fish protein is the best at supplying all the essential amino acids, although there is one non meat and strictly speaking, not vegetable, that contains every essential amino acid.