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Picking The Right Tank For Hermit Crabs

Updated: Jul 7

Despite what most people think, Hermit Crabs NEED lots of space!! Crazy right? No mate, your Hermit Crab cannot live in an empty fishbowl... I'm not even sure your fish can live in a fishbowl.

They may be small creatures, but they require plenty of space to live happily, safely and comfortably.

So why do Hermit Crabs require so much space? Let's face it, all Hermit Crabs in captivity came from one place... the beach! Yep, unless you have successfully bred your own crab, every crab that anyone in Australia owns was plucked from the wild. And in the wild, they have a zillion kilometers of space to roam freely and dig down to moult. Because of this, they often do not have to worry about where they would dig down to take their moults, with the amount of space in the wild, the chances of coming across another crab are slim.

But in captivity, it's an entirely different ball game. Our crabs are confined to a certain amount of space, and within that space, there is only so much room to dig down and moult safely.

If a crab happens to come across another crab who is mid moult, there is an extremely high chance that they will take this opportunity to consume their tank mate while they are in a weakened state. And when we say consume, we mean eat them until the crab is dead. Grim I know.

How much space should Hermit Crabs have?

Hermit Crabs need at least 38L of space PER crab. That's right. If you want to house 2 Hermit Crabs, you're going to need a 76L tank minimum.

The easiest way to calculate how many crabs you can fit into your tank is by using the below formula.

Tank litres ÷ 38 = number of crabs you can house.

(76 ÷ 38 = 2)

This formula is great if you already have a tank and know the litres.

If you are planning to get a tank, or upgrade from a small tank to a big tank and you already have crabs, you can use this formula instead. Although both will give you the same answer.

Number of crabs x 38 = how big your tank should be

(2 x 38 = 76L tank)

Both formulas tell you that you can fit 2 crabs in a 76L tank or need a 76L tank to fit 2 crabs. If you're bad at math (like me) just use your calculator, no need to work that tired brain overtime.

What happens if you overcrowd your tank?

Overcrowding is never recommended. Maybe you can squeeze just one more tiny crab in but squeezing in 2+ more crabs into an already full tank is just asking for trouble.

Although they live in large colonies in the wild, they have plenty of space to get away from each other to safely moult.

Overcrowding can often lead to stress, fighting over shells and foods, and most commonly, death. I'm sure you're wondering what are the chances that a crab would be found during moulting? And can't a crab be found during a moult even if the tank isn't crowded? True! BUT there is a much less chance of them being found if they all have their own 38L of space available. During moulting, Hermit Crabs give off a fresh scent, this attracts other crabs to them as food (this is why we always stress that surface moulting crabs should be isolated) moulting is something that all crabs must do on their own, it's definitely not a shared activity (no matter how much they like each other)

By offering plenty of space, the crabs moulting scent is harder to trace by nearby crabs.

What kind of tank should I be looking at?

Firstly, let's talk about the tanks you SHOULDN'T be looking at. Tanks that should be avoided as they do not offer a suitable environment for your crabs.

• Krabooz Plastic "Mansion" & Donut

• Fish Bowls

• Hermit Crab advertised tanks at pet stores

• Tanks with no lids

• Tanks with "breathing holes" in the lid or sides

• Mesh tanks

• Tanks with wooden lids

• Tanks with mesh

• Wire cages

• Reptile tanks (some of these can be altered to be suitable, but with the money you're spending to do it up, you're better off just buying the right tank from the start)

• Small fish tanks with a hooded lid

Why do the above tanks not offer a suitable environment?

As you probably already know, Hermit Crabs need high heat and humidity to survive. As well as deep moist substrate for moulting. Tanks with gaps, no lids, holes etc. will not hold heat and humidity well.

Small tanks or oddly shaped tanks (like a fishbowl) will not hold deep substrate for moulting.

All you really want (and what your crabs really want) is a simple all glass fish tank with a glass or Perspex lid.

You don't need to go out and spend hundreds to thousands of dollars on brand new glass tanks, secondhand fish tanks are where it's at!

Search your local community boards, Facebook Marketplace or Gumtree for secondhand fish tanks. Usually, you can find a bargain! I have been lucky enough to get a huge 6ft tank with a custom-made wooden stand for $600, and 2 x FREE 4ft fish tanks with stands. Just keep searching online for tanks until you find one big enough.

Alternatively, and if you don't want to wait, you can purchase a brand-new fish tank from a local pet store or aquarium. It doesn't need to be fancy, and you don't want a tank that has a hood as the lid. These are not sealed well and usually come with air vents, Hermit Crabs can also sometimes climb up into the hood and if there's a way out, they will find it.

Sometimes tanks don't come with a lid, and this can be super frustrating. Thankfully, lids are very quick and easy to make. All you need is a Perspex sheet from Bunnings, a Jigsaw Cutter and a Perspex blade. Measure the top of the tank where the lid will sit and cut your Perspex to fit, you can also cut a small corner piece off to make room for bubbler cords and for easier access to open the lid when needed.

How can I calculate the litres of a tank?

There is a formula for calculating your tank litres, but if you're like me (no good at math) I find the easiest way is to take the tanks measurements and put them into a tank volume calculator. This is the website that I use whenever calculating tank volumes.

Simply measure your tanks length (across the front of the tank), the tanks height (from the base of the tank to the top), and the tanks depth or width (from the front of the tank to the back of the tank) and add these into the tank volume calculator.

Do we count the litres of the sand or just the litres of the tank?

When calculating the space for hermit crabs, we do not count the litres of the sand. Only the litres of the tank. It's strange to think why we wouldn't count the litres of the sand, but crabs use the space above the sand too and they still need enough space above the sand to move around, change shells, eat, play and feel safe and secure.

Don't hermit crabs need gaps in the lid to breathe fresh air?

Definitely not. Hermit Crabs do not breathe fresh air, they do not have lungs like most animals do. They absorb oxygen in humidity through their modified gills. If you have air holes in your tank, humidity will escape, and your crabs will struggle to breathe.

What if my secondhand tank is not watertight? Is that okay?

Yes, that is fine. Your tank is only holding sand and pools. It is not being filled with water. If you come across a secondhand tank that is not watertight (not safe for fish) it can still be used for a crab tank.

Is a tank stand really necessary?

No, tank stands are not a must have. However, they do make storing your tank much easier and neater. Tank stands are built to carry the weight of a tank full of water, meaning they can easily support a tank that is half filled with sand. Stands are usually slightly larger than the tank so the tank will fit securely in the top part of the stand, meaning less chance of being knocked.

You can still place your tank on other support systems such as shelves, cabinets etc. Just make sure that your entire tank is sitting on its support and not hanging over the sides or front/back. A tank that is hanging over the side of its support will put pressure on the base of the tank and can cause cracks.

My tank has a crack, is it still safe to use?

That depends where the crack is and how you fix it. If it is particularly large, it will weaken the structure of the glass tank.

Cracks should be dealt with as soon as they are discovered. You can either tape cracks with strong tape or glue another piece of glass or Perspex over the top of the crack to help prevent it spreading further. Depending how bad the crack is, you may need to replace the tank entirely.

What NOT to do with your tank

• Never lean against your tank, this can cause pressure and if on a stand, can cause the stand to fall or buckle.

• Never try to move a tank that is full of sand, this will cause a great amount of strain on the base of the tank and more than likely crack the base of the tank.

• Never try to move or travel with a tank that has hermit crabs in it (especially ones beneath the sand) the movement of driving or moving the tank around will cause the moult caves to collapse, killing your moulting crabs. Always empty a tank before moving it.

• Never use cleaning chemicals on a tank that houses hermit crabs. These are toxic and can make your crabs very sick.

Cleaning a secondhand tank

The best cleaning products for cleaning a secondhand tank includes the following.

• Dishwashing liquid

• Vinegar diluted with water

All of my tanks are secondhand and have all been cleaned thoroughly before bringing inside. Below I will go over the way I clean my tanks to make them look brand new, as well as cover other ways to clean them.

Dishwashing Liquid

  • I always clean my tanks outside on the grass, this way I can be as messy as I want. Using a pressure washer, I will rinse the entire tank inside and out to remove any debris.

  • Squirt some dishwashing liquid inside the tank (not too much or you will have bubbles for days) and give the entire tank a really good scrub with a NEW dish scrubber (don't use a secondhand dish scrubber) this takes a bit of Elbow grease depending how dirty the tank is.

  • Using the pressure washer, rinse all of the soap off the tank until there are absolutely no bubbles. You may need to move your tank onto its side to rinse the soap out.

  • Once you are sure there is no more soap, take a towel or a microfiber cloth and dry the tank. This will also remove any excess dishwash liquid that you can't see.

If you don't have a pressure washer, that's fine (I steal my husbands) you can simply use the garden hose.

Diluted Vinegar

  • Dilute vinegar 1 cup of vinegar to 1 cup of water and spray all over the tank. Leave for up to 10 minutes and use a NEW dishwashing scrubber to scrub the tank clean.

  • Rinse the tank with water to remove any excess vinegar and dry with a microfiber cloth or towel.

  • This method can sometimes leave a strong-smelling vinegar smell.

Removing hard scale water stains

  • These can be an absolute pain to remove, firstly spray vinegar directly onto the water stains and let it sit for 20 minutes.

  • Using a NEW dishwashing scrubber to scrub away the stains.

  • If this still doesn't work, you can use a razor blade to gently scrape away the stains.

Do I need to use prime in the water to clean my tank?

No, you do not need to use Prime in the water that you use to clean your tank. This ends up being a huge waste of Prime and money.

What NOT to use on your tank

  • All-purpose cleaner

  • Mirror or window cleaner

  • Any form of glass cleaner

  • Orange Oil

  • Essential oils

  • Any chemicals

  • Abrasive scrubbing pads

  • Steel Wool

If you wish to remove fingerprints, smudges, water marks or sand from inside or outside your tank, simply use a damp cloth. Chemicals are very toxic to hermit crabs and can make them very ill, sometimes resulting in death.

Altering Reptile One or Exo Terra Reptile Tanks

These kinds of tanks can be altered to create a suitable environment. But they require a bit of work. The front door sits too low on the tank to have a suitable level of substrate. You can however use a piece of Perspex cut to size and glue it along the front of the tank, keeping in mind that your substrate needs to be a minimum of 6" or deeper. These reptile tanks also usually come with a side panel that is made of mesh, this will also need to be covered securely with a piece of Perspex cut to size. You can glue this to the inside or outside of the mesh to cover it. The lid is also made of mesh. This can be removed entirely and replaced with a piece of Perspex or glass cut to size. It is important to cover the mesh parts of the tank to ensure that heat and humidity do not escape.

  • You can see that the owner of this tank has added a piece of Perspex panel to the front of the tank, this way they can have deeper substrate without it falling out the front of the tank when opened.

Handmade Tanks

Some owners are so crafty, they have even gone as far as creating their own tanks out of everyday objects! We have seen one incredible tank created out of a wooden cabinet with glass and wood doors. As long as these are created the right way and with a lot of patience and precision, it can be done! It took a lot of work for the owners to seal the wood to stop it from rotting, and ensure the tank is airtight and keeps its heat and humidity. Take a look at the tank below!

There have been cases of other owners creating their own tanks out of Perspex sheets. As long as you seal these properly, so they don't leak or fall apart, this is also another option for a DIY tank. Take a look at a handmade tank below.

  • This tank has been 100% handmade using Perspex panels.

A glass fish tank below, using a Reptile One tank as a topper.

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