How to Set Up a Freshwater Crab Tank

How to Set Up a Freshwater Crab Tank

Owning a freshwater crab can be a very worthwhile and unique experience. So, if you are looking to add them to your pet family, in order to offer them a safe environment, it is important to do research on how to take care of crabs and how to set up a tank for them.

Luckily, setting up a freshwater crab tank is relatively easy even for beginners. The process and principles will be the same for all crab species. Just keep in mind that not all freshwater crabs are fully aquatic and prefer paludarium setups.

This guide will cover important steps you should take in order to set up the ideal environment for your crab, it will also state the importance of water cycling and give you some practical tips for taking care of your new friends.

Let’s get started.

Step 1: Picking Your Crab’s Tank

Empty shrimp tankThe size of your chosen tank depends on the crab species. It should not be less than recommended.

For example, 5 gallons (20 liters) is the lowest volume of water needed to easily establish the nitrogen cycle. Bigger tank is easier to maintain than small ones because the larger water volume dilutes the waste products.

Second, it may be close to impossible to create a proper landscape for a crab in small tanks.

Third, many crab species are territorial, so, there is a very high chance that it will cause an aggression if you decide to keep several of them.

Therefore, whenever it is possible, always opt for a bigger size. After all, you want to own a happy and healthy crab – you want it to thrive, not survive!

The BIGGER the tank the better.

Most popular freshwater crab species Tank size
Minimum requirement
Thai Micro crab 5 gallons (~20 liters)
Rainbow Crabs 20 gallons (~90 liters)
Pom Pom Crabs 5 gallons (~20 liters)
Vampire Crab 5 gallons (~20 liters)
Tanganyika crabs  10 gallons (~40 liters)
Panther crabs 20 gallons (~90 liters)
Matano Crab 20 gallons (~90 liters)
Tangerine-head crab 5 gallons (~20 liters)

Tank and Lid

Almost all crabs are great escape artists. They are known to climb out and when they do so, they often fell onto the floor breaking their legs or carapace.

In addition, their gills need moisture, otherwise, the crabs will essentially suffocate with time.

So, a tight-fitting lid is essential. 

Nonetheless, even if your tank does not have a lid, you can create one yourself. It can be plastic, acrylic, or placing netting or mesh over the top of the tank.

Shape of the Tank. Length Over Height

There are lots of tank models on the market. However, I would strongly recommend that you should also be looking for tanks which have more length than height. It mostly concerns small tanks; large aquariums should not have this problem.

The reason for this is because crabs need mostly a place to crawl from side to side, not up and down.

Location of the Tank

Find a good location for the tank. It should be away from air vents and windows that get direct sunlight. At the same time, the tank should be near an electrical outlet in the area that able to tolerate a water spill. Unfortunately, it happens to the most careful of us!

For more information, you can also read “7 Tips for Shrimp and Fish Tank Location”.

Tank Stand

You’ll also want to get a stand to put the tank on. A good stand will support the number of gallons you are going to have.

Make sure it is level so there is no potential to be knocked or tipped over.

Step 2: Cleaning, Testing and Painting Crab Tank

DO NOT underestimate this step, do not skip it! It can be absolutely spirit breaking after setting up your crab tank to find out that it is leaking or there is some kind of residue which is toxic to the crab.

  • Cleaning is a very simple process. You need something that will decompose fast and will not leave any trace in the tank.

shrimp tank Hydrogen PeroxideFor example, it can be Hydrogen peroxide (H2O2). This is a cheap and handy household supply that we often use for cleaning and disinfecting.
Spray it on the walls of the tank, and let it sit for 10 – 20 minutes. After that, wash it off properly a few times to remove hydrogen peroxide. Do not use soap, only tap water!

Note: Read instructions and use gloves for safety when you are working with Hydrogen peroxide

  • Leaking Test. Do a leak test by filling the tank with water for 24 hours.
    Tip: Put some paper underneath the tank. If you do not see any wet spots on the paper, the tank is safe.
  • Painting. This is optional but I always strongly recommend doing that anyway. The point is that according to some studies, a dark background can improve the crab coloration.
Hydrogen peroxide – check out the price on Amazon

Step 3: Adding Substrate to the Crab Tank

The substrate refers to whatever we are going to put on the bottom of the tank.

Substrates will allow crabs to make dens under aquarium decorations where they will readily retreat if overly threatened, or scared. They will also stay hidden in these dens for multiple days while they molt.  

In addition, it hosts loads of beneficial bacteria, that will help stabilize your water parameters.

Ideally, substrate should mimic their natural habitat.

The substrate should not be too thin or too deep, for example, 3 – 4 inches (or 7 – 10 cm) will be good enough for most crab species.

Using Sand in Crab Tank Setup

How to Set Up a Crayfish Tank - substrateCrabs enjoy to burrow, dig and push everything around. If you think that they will not change anything in your tank, you are wrong!

They will definitely rearrange the substrate to make small mounds or to make caves to hide in. Therefore, sand would be one of the best substrate for crabs due to their digging needs.

Tip: When you are picking a sand color, you should keep the color of your crab in mind. For example, darker-colored species will stand out with a lighter colored sand backdrop. However, sand is a great substrate for a crab tank.

For example, sand substrate: 

CaribSea Super Naturals Crystal River Sand – link to check the price on Amazon

Using Small Gravel in Crab Tank Setup

Using small gravel will still allow your crab to burrow, dig, sift and rearrange everything to their liking. In addition, gravel comes in a variety of different colors. This makes gravel a great choice aesthetically for any tank.

For example, gravel substrate:

 Seachem Flourite Black Clay Gravel – link to check the price on Amazon

Would Soil Substrates Be Suitable for a Crab Tank Setup?

Soil can be used in crabs set ups, however, in my opinion, there is no need for it because we are not planning to add plants that require it to grow. 

In addition, soil substrates are often active substrates. Active (buffered) substrate – this is a substrate that alters water chemistry (PH) and keeps the pH at a steady low level.

It is not good for the invertebrates because too low pH and very soft water can cause molting problems for your crabs.

Another potential problem is that some soil substrates leach ammonia for some time. So, it will require extra time and work to deal with.

As a result, even though, it is still possible to keep crabs in such tanks, it is not the easiest option.

Freshwater Crabs in a Bare Bottom Tank

You do have the option of keeping your crab tank bottom bare. However, you will lose out on watching them act as they normally would in their natural habitats.

On top of that, I can also add that your crab will be very unhappy and stressed. Therefore, unless it is a quarantine tank, I would never recommend a bare-bottom tank for crab. 

Prepare the Substrate

Do not forget to clean and rinse sand or gravel to get rid of any debris or dust that might have been accumulated on it. Sand requires more work than gravel. If you forget to rinse your sand, your tank can turn into an uninhabitable cloudy disaster.

You can’t skip this step. Sand will normally turn tank water cloudy but it will settle over time. If you do skip rinsing the sand, your tank can become a cloudy mess that won’t settle for weeks or even months!

Note: Even if you see on the bag it is marketed as “pre-rinsed” or “pre-cleaned” by manufacturers. DO NOT believe them. Although the substrate itself can be clean, the bags often contain dust, debris, or other residues. We do not need any of that in our crab tank.

How to Prepare Sand for Crab Tank

  • Put your sand into a bucket and spray the sand with a hose.
  • The excess water will run out of the bucket and the water will be cloudy and dirty initially.
  • With continuous rinsing, you will begin to notice that the water will run clearer.
  • A clear stream means that the sand is ready to add to the tank.
  • Important: When you think that sand is absolutely clean – rinse it again! Sand has lots of tiny detritus particles.

Tip: It is easiest to add sand to an empty tank. Use some sort of surface, such as plates, to prevent stirring up the sand when you begin to fill the tank with water.

How to Prepare Gravel for Crab Tank

  • Place the gravel into the bucket.
  • Fill the bucket with tap water. The water should completely cover the gravel.
  • Stir and move the gravel around (use a stick if necessary).
  • Leave it in the bucket for 5 – 10 minutes. It will soften up any dust and debris that may be on the gravel.

Step 4: Adding Decorations and Plants

shrimp tank Break, cones driftwood cocnutFreshwater crabs are very active creatures that enjoy digging, pushing, pulling, and climbing. Most of the time you will see them crawling everywhere and exploring everything. The more you give them to explore, the more they will venture out and get active.

Supply your crabs with decorations, driftwood, rocks, plastic tunnels, crab huts, fake plants, etc.

All these decorations play important roles in crab tank setups:

  • They replicate their natural environment, therefore, it will let them feel at home.
  • They provide a lot of hiding places to reduce stress (during molting) and territorial battles.

Panther Crab (Parathelphusa Pantherina)That is why adding decorations is not just recommended option, they are vital.

Make sure that any rock or decoration that you put in your tank is aquarium safe. Do not take a random rock from outside and put it into your tank as a decoration. The rocks may contain unseen bacteria or leach unwanted substances that can affect your crab.

Tip: If you are planning to have a budget set up for your crab, use PVC pipes. I can tell you that your crabs will love them! The only downside is that they do not look esthetically pleasing. Of course, do not forget to clean them and don’t use soap!

Examples (links to Amazon): 

Plants

Water Sprite (Ceratopteris thalictroides) floatingUnfortunately, many crab species and planted tanks are not compatible (except, Thai Micro crab, Pom Pom Crabs, Vampire Crab, and a few other species). The point is that they are highly skilled at uprooting, cutting, and consuming plants. 

Therefore, if you plan on placing your crabs into tanks with live plants, you should be aware that they will view them as food. Tough plants such as Java ferns might have a chance to withstand their attacks, but most others will be destroyed or damaged.

The only plants that crabs tend to leave alone are floating plants because they simply cannot get there or fake plants.

Important: If you decide to add fake plants, take a look at the material they are made of. Avoid soft plastic or soft rubber. Crabs will try to chew and eat it.

Step 5: Install Aquarium Filter

How to Set Up a Freshwater Crab Tank - filtersEven though many freshwater crab species come from still waters, you must use a filter. It will help keep your tank clean, keep the nitrogen cycle running, and reduce the amount of harmful bacteria that can lead to crab diseases.

There are plenty of filters on the market: sponge filters, hang on the back filters, canister filters, internal filters, sumps, undergravel filters, fluidized bed filters, etc.

So, what filter is the best for the crab tank setup? It can be really confusing, especially, if you are new to the aquarium hobby.

Considering the needs of our tank setup, such as: water circulation, ease of use, safety, and budget – I would recommend take a look at canister filters or hang on the back filters.

Important: Crabs are destructive by their nature. They will try to tear apart everything they find in the tank. That is why the sponge filter is a big NO. Another problem, they will chew and try to eat small pieces of sponge. It can be detrimental to their health.

When choosing a filter, it will be better to choose one which has a slow or adjustable flow. These are going to be the best ones for the job and can help create the ideal environment.

Tip: if you have a 10-gallon (40 liters) tank, choose the filter, which is rated for at least 20 gallons (80 liters). The difference in money is minimal but the benefit is huge!

Examples (links to Amazon): 

Step 6: Install Your Air Pump and Heater

Aquarium air pumpMost freshwater crabs will be absolutely fine if your temperature is in the range of 20 – 24 °C (68 – 74 °F). Basically, we can say that they do not need a heater. 

However, it only takes one big fluctuation in temperature or a cold day, to drastically reduce the warmth in a tank that can potentially cause your crab to suffer from temperature shock.

Therefore, if there are temperature fluctuations in the place you live, it can be a good idea to have a thermostat heater. Thermostat heaters work by maintaining a set temperature. Once the temperature goes below a certain degree, it turns on.

Freshwater crabs need oxygenated water. Nothing fancy, any air pump will be good enough.

Important: Unlike filters, only choose the heater appropriate for your tank size. If the heater is larger than what your tank actually requires, it may lead to overheating and ultimately – the death of your crab.

Note: I strongly recommend using only adjustable heaters. It is just more practical. If you have a preset heater in your tank and it’s not heating it to the proper temperature, then there’s no way of adjusting it if it’s preset.

Examples (links to Amazon): 

Step 7: Installing Aquarium Light

All crab species are nocturnal creatures. So, they do not have any special requirements.

Basically, the lighting is mostly up to your taste and how well you want your tank to be illuminated.

However, if you want to keep even floating plants, lighting should be adapted to the needs of plants in your tank. Ideally, you need to want to buy lighting that you can change the setting on.

You can read more about it in my articles:

Advanced Guide to Planted Tank Lighting. 

Step 8: Filling up the Aquarium

Place a plate on top of your substrate, and slowly pour water on top of the plate to fill your tank. We do that to reduce disturbance and clouding issues. The point is that if you pour water directly in, then you’re going to have a complete mess! 

When you are filling your tank make sure you give your crab about 1 – 2 inches (2.5 – 5 cm) of space at the top. It will reduce the chance of your crab crawling out.

After that we just let the tank clear up and get cycled (established).

Step 9: Cycling Your Crab Tank

How to Set Up a Freshwater Crab Tank - Nitrogen Cycle DiagramThis is the most important step! If you skip it there is a very high chance that your crab will simply die. Without a colony of beneficial bacteria to process the waste, your crab will very quickly poison itself. 

So, the goal of the Nitrogen cycle is to build up beneficial bacteria in the tank. These beneficial bacteria are used in the tank to break down harmful waste (ammonia) into a less toxic form, first to nitrite and then down to nitrate. Once this cycle is done your tank should not have ammonia and nitrites.

There are three main methods of cycling the tank:

  1. By adding filter media with beneficial bacteria from another tank.
  2. We can sit back and be patient as the tank will have to cycle for a month or more by itself.
  3. We can add some beneficial bacteria to boost the cycling process.

If you are an experienced hobbyist and already have another tank. Obviously, the first method will be the optimal way for you.

As for the second method, if you are new to the hobby, and have some time, there is nothing wrong to wait. 

However, if you want to boost the cycling process, you will have to buy bacteria starters.

Once you have dosed the tank with enough bacteria, give it some time to develop and check the parameters to see if the ammonia and nitrite are at 0 ppm. You will have nitrates, this is normal, to lower them – do a water change.

Some recommended products (links to Amazon):

How To Setup an Easy Quarantine Tank beneficial bacteria

You can read more about “Step-by-Step Cycling your Shrimp Aquarium Fishless” right here. 

Water Testing Kit

API test kit for shrimpYou’ll need the Test Kit to monitor your cycling process. Without a test kit, it will not be possible to estimate the real condition of the growing nitrogen cycle (ammonia, nitrites, and nitrates, which are poisonous to crabs.

Therefore, the test kit is a must-have tool! I am pretty much sure that you cannot get away without it for a long period of time.

There are 2 types of test kits:

  • the test strips
  • the liquid tests.

Personally, I would highly recommend using a liquid test as they are more accurate than the test strips.

Recommended product (links to Amazon):

Step 10: Adding the Crab to the Tank. Acclimation

Once the cycle is finished and the water parameters are met, technically, you can add crab.

However, if you want to play safe, it will be better to wait at least 1 week more. We need to be absolutely sure that water parameters are stable and there are no sudden ammonia spikes. Do not forget to check your water parameters daily.

Acclimation

When you bring your crab home, it will come in a plastic bag or container of water. 
Do not put it directly in the tank!  You can shock the system of your crab by changing water parameters and temperature too quickly.

Therefore, you need to slowly acclimate the crab before releasing it into their new home.

Read more about it in my article How I Drip Acclimate Shrimp and Why” the principle is absolutely the same.

You can add your crab now!

In Conclusion

Even though freshwater crabs are somewhat unorthodox pets, more and more hobbyists are giving crab keeping a try.

Setting up your freshwater crab tank can be somewhat intimidating, but it is not difficult and can be easily done even by beginners.

With a bit of research and investment of time and resources, anyone can recreate the ideal conditions for crabs to thrive in their new home.

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