Sargo are bottom feeders, and prefer crustaceans as their staple diet. The most reliable choices for bait include shrimp/prawns, mussels, squid, clams, and sea snails.
People also catch them with worms, and small pieces of fish. Where they're plentiful, they'll eat other bait that people have on hand when catching similar fish in the same water.
There's also another paste in addition to the one you mentioned. It's made from bread/flour and cheese, and the sargo seem to enjoy it.
Sources for this information:
How to Catch a Sargo
Seafishing Marine Species
The Outdoor Lodge