* Hermit crab size: Hermit crabs come in various sizes, and the size will determine how much space they need.
* Substrate depth: You need a good amount of substrate (like coconut fiber) for them to burrow and hide. The depth of the substrate will affect how much usable space remains.
* Decorations: Providing hides, branches, and other decorations for enrichment takes up space.
* Social dynamics: Some hermit crab species are solitary, while others prefer being in groups. It's important to research the specific species you are interested in to determine their social needs.
Instead of focusing on a specific number, it's better to consider the following:
* Space per crab: Aim for at least 1 gallon of tank space per adult crab.
* Vertical space: Hermit crabs like to climb, so make sure your tank is tall enough.
* Substrate depth: Aim for at least 4-6 inches of substrate.
* Proper enrichment: Provide plenty of hides, branches, and other decorations to keep them stimulated.
In general, a 20-gallon tank is a good starting point for a small group of hermit crabs (3-5) if you provide adequate substrate depth, decorations, and vertical space.
It's important to research the specific species of hermit crab you are interested in to determine their individual needs and ensure they have enough space in your tank.