With gold nugget plecos you should feed a bit more protien than the more common species. Alternate with the plecos tabs, fresh veges and some meaty food like prawns or bloodworms.
With the pleco tabs, if they eat them all right away, give them another one. If there are bits left in the morning, then you fed too many, cut back by one.
With meaty food feed small amounts and make sure it gets eaten fairly quick to avoid water problems.
Veges are the easiest to feed, drop in a chunk, let them eat their fill overnight and take out the leftovers in the morning.
Cheers
Ian