Are crustaceans carnivores

Crustaceans are organisms under the subphylum crustacea, encompassing over 50,000 species. Their eating habits are not all the same, so you can not make a general statement.

Mantis shrimp are carnivorous hunters, copepods are often herbivorous, caridina shrimp are often omnivorous scavangers... It would be better to refine the question further.

I wish I could give you a reliable general statement, but I don't know the 50,000 species, haha. Sorry!