A few are eurythermic, but most have a narrow range of acceptable temperature. Many species prefer strong currents that bring their food supply to them, but the energy of the environment cannot be too strong for the lacy forms because it will break them. Most species need a hard substrate to initially attach themselves. Some are quite selective about the nature of the substrate. A few have adapted to muddy bottoms.
Bryozoans dislike siltation and prefer clear water.
They live from tidal depth to deep-water, but most live in the sublittoral zone. The greatest abundance is at 20-80 meters. Many are found in the photic zone, but they are not dependent on light. Although they are small, they are able to attach to the bottom and were often found bridging gaps between other organisms and serving as sediment traps for fine sediment. Modern coral reefs often include abundant encrusting bryozoans.