Do Crabs Like a Sandy Bottom or Grass?

The crab family contains thousands of land, freshwater and ocean species. Their diversity dictates various substrate preferences, including rocks, sand and vegetation. General guidelines hold true for most groups of crabs, but study up on the exact species of crab you want to keep.

  1. General Guidelines

    • Most crabs prefer sandy substrate, including both land and water crabs. However, some land crabs prefer some plant matter mixed in with their substrate. Grass makes an inferior substrate to other plant materials like coconut husks, since it can rot and foul the substrate.

    Hermit Crabs

    • Hermit crabs are technically not true crabs, but their care and physiology overlap those of true crabs in many ways. Terrestrial hermit crabs need deep substrate to burrow in, at least as deep as the hermit crabs are tall. Sand works well; sand mixed with coconut fibers resist compaction better. Marine hermit crabs prefer either a sandy substrate or a rocky one.

    Freshwater Crabs

    • Freshwater crabs, including freshwater fiddler crabs and red-clawed mangrove crabs, usually prefer a sandy substrate, preferably with some dry land to crawl onto. Most freshwater crabs do their best in tank of just one species, since they may eat fish and vice versa, depending on the size of the fish. Additionally, most species of freshwater crab actually prefer brackish water. Brackish water is water with more salt content than freshwater has but less than full-strength seawater.

    Reef Crabs

    • Many tiny, relatively peaceful crabs have found their way into the marine aquarium hobby. Crabs who do not pick on coral, like emerald and guard crabs, have no strong preference about substrate. These species spend most of their time moving among corals on rocky surfaces in aquariums. Many marine hermit crabs have similar habits and won't spend much time on the substrate. For these species, the substrate does not matter. Most marine aquariums feature sandy or rocky substrate.