OP, Yes, adding a gold nugget would over stock your aquarium, by 31% according to aqadvisor.
If I where you, I would up the number of tetras instead to 5+, and look into a smaller sp of pleco.
Keep an eye on those gouramis, as they could start fighting with each other.
"And 5, very important 5... Don't let me eat pears.. I HATE PEARS."