Setting up an Isolation Tank for molting

2.5gal ISO

Every crab owner needs to have a Isolation Tank, or ISO, on hand. Not only does it provide an environment for molting if that is your chosen method, but it should be used as housing for newly purchased crabs. The size of the ISO depends on the size of your hermit crabs. Small crabs only need about 6 inches of substrate, while jumbo crabs need a 10 gal tank with 12 inches or more of substrate. The crab needs enough room to dig down and create a subterranean cave. It also needs room to spread out and push off its exoskeleton. The ideal container for a ISO is a glass tank or aquarium. If your main tank is large enough to place a small plastic ISO inside of it, that is acceptable. Your ISO will need an overhead light also to maintain a normal cycle of light and dark.

Type of tank:

  • A glass tank ranging from 2.5 gallons to 10 gallons with a lid
  • A plastic Kritter Keeper with Saran Wrap on the lid
  • A plastic bucket or bowl with a lid, vent or puncture to allow air exchange

Gauges needed:

  • Hygrometer
  • Thermometer
  • Hygrometer
    thermometer at substrate level

Types of lid:

  • Glass
  • Acrylic/Plexiglass
  • Screen lid with Saran Wrap

Types of substrate:

  • Playsand
  • Forest bedding/Eco Earth
  • Mixture of the two

Eco EarthISO

Type of heater:

  • Under the tank heater for a glass tank
  • Plastic containers can’t be heated, which makes them a poor choice for a ISO unless you can place them within your main tank, or find a room that is warm enough to keep the ISO warm also.

You will also need a light source. This can be your heat source as well.

ISO temperature should be between 75-80F This should be the substrate temperature not the air temperature. The humidity should be 75-80% Relative. Don’t guess, get the gauges! Place them close to the substrate surface because that is where the crab is going to be, not at the top.

Offer food and water until the crab digs down. After that it is unnecessary until it surfaces. Gently smooth the surface of the substrate so you will know if your crab comes up.

ISO’s should be placed somewhere quiet. But a normal cycle of light and dark should be maintained. Light is critical to a crabs ability to metabolize and this is how a hermit crab regulates it’s body.

Signs your crab is ready to molt:

  • Digging
  • Consuming large amounts of water or soaking in the dish
  • Cloudy Eyes
  • Ashy looking exo
  • Lethargy (very in active)
  • Spilling water to dampen the substrate

Some crabs display NO symptoms at all and will surprise you with a surface molt. Protect this crab by cutting the top and bottom off of a 2 liter pop bottle, then gently push it down around the crab. Push it all the way to the bottom to prevent other crabs from climbing over or digging under. Do not attempt to move or dig up a molting crab. Do your best to protect it and let nature take its course.

Molting Article by Sue Latell of

PPS: Minimizing the impact by Sue Latell of

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