Many bacteria (monerans) and fungi are decomposers. Thus these groups are ecologically similar.
Producer protists are unicellular. Many of them produce their foods using sunlight and CO2. Like green plants, producer protists contain chlorophyll a, chlorophyll c pigments, peridinin, and diadinoxanthin pigments. Zooxanthellae (dinoflagellates) are mostly photosynthetic protists. Some protozoa synthesized their food using chlorophyll pigments in presence of sunlight, and CO2. Example: Euglena (Euglena gracilis) an Dinobryon (Dinobryon divergens)
On the other hand, consumer protists are heterotrophs in nature. Consumer protists obtained their nutrition and energy from organic materials. They consume other organisms. Protozoa such as Amoebas ingest solid particles through phagocytosis. During phagocytosis, the plasma membrane invaginates inward to engulfs a food particle. Then the food particle surrounded by a membrane is pinching off intracellularly to form a food vacuole.
Fungi are eukaryotic heterotrophic organisms. They are nonmotile organisms, and the cell walls contain chitin. They are multicellular organisms (few are unicellular: yeasts). Most of the fungi are saprophytes in nature. They obtain nutrition and energy from wastes and dead/decaying organic matter. Saprophytic fungi act as decomposers. Example: Mushrooms.
Organisms in the Kingdom of Monera are Prokaryotic in nature. They are unicellular, and the true cell nucleus is absent. Examples: Archaeobacteria, Eubacteria, and Cyanobacteria. Many bacteria are saprophytic in nature. They obtained their nutrition and energy from the dead/decaying organic matter.