Skip to Content

Why is my Snail Turning Black? (With 4 Easy Solutions)

Disclosure: When you purchase something through my affiliate links, I earn a small commission. As an Amazon Associate, I earn from qualifying purchases.

I tend to worry when I see my snails change color. That applies to those times when I caught my snails turning black. Over the years, I investigated the issue and learned why it occurs. I also found some valuable techniques to reverse the annoying phenomenon.

Snails typically turn black due to inappropriate water conditions, such as elevated ammonia, nitrates, pH, and copper. However, snails also tend to blacken when they reach adulthood, especially those reared in aquariums. In some cases, it is merely Black Beard Algae that grew on the snail’s shell.

As we move forward, I will share four steps you should follow when you notice that your snail is turning black. That includes testing your aquarium’s pH, ammonia, nitrates, and nitrites levels, using the well-known API Aquarium Test Kit (link to Amazon).

Why is my Snail Turning Black?

Snails come in a variety of colors, including black. However, if your snails started as a different color but now they are turning black, one of the following factors might be the cause:

1. Your Snail Merely Matured

How old was your snail when you got it? Snails tend to change color as they grow. They don’t have much of a color when they first hatch. Over the next few days, you may notice certain tinges. But you cannot assume that a snail has settled into its final color until it reaches adulthood.

If you have a young snail on your hands, the creature is probably turning black because it finally adopts its true color. It isn’t always possible to predict the color a snail’s shell will manifest. However, experts in this field will tell you that the rate of growth affects the color as well as the thickness.

Snails that live in tanks tend to develop lighter colors. They have a safe and comfortable home, not to mention access to all the food they want. This allows their shells to grow at a faster pace. And the faster the rate of growth, the thinner the shell, and the lighter the colors.

The opposite is true for snails that live in environments where food is scarce. Their shells grow slower, thicker, and darker. This is why snails from the wild are normally darker in color than those reared in aquariums.[1]

2. It’s Black Beard Algae

Black beard algae can cling to any hard surface it finds in the aquarium. That includes the walls, filters, rocks, pots, and even snail shells.[2] You can find it in both saltwater and freshwater aquariums.

Black beard algae start as small spots on various surfaces before taking on the appearance of hair patches. It can hitch a ride into your tank on plants and decorations that have been contaminated.

That type of algae may induce stress in fish, especially when it starts covering their hiding places. But it won’t harm your snails. However, it can create the illusion that the creatures turn black once it starts covering their shell.

3. Injuries & Stains

Like most hard surfaces in the tank, snail shells can pick up stains because of interactions with other objects or as a result of injuries. For instance, a collision with a hard object may bruise a snail’s shell, forcing it to take on a darker tone.

Stains are easy to identify because they don’t spread. The black spots, patches, and smudges will remain localized to a particular location. Pay close attention to the behavior of the snail. If it maintains a happy and healthy demeanor, the stains are not a cause for concern.

4. Inadequate Water Conditions

Most anomalous symptoms in aquatic creatures can be traced back to poor water conditions. Snails are no different. They are sensitive to water with the wrong parameters, not to mention elevated toxins like ammonia and copper.

Poor conditions in the tank usually strip a shell of its color. But you cannot always predict a snail’s response to poor tank conditions. Discolorations are a common symptom of a poorly maintained tank.

How to Treat Snails That Turn Black?

If your snail is turning black, your first step should be to test the water’s parameters. The poor conditions in your tank will either change the color of your snail or exacerbate the factors causing it to turn black.

Either way, you have to test the water. Make sure the temperature (68 to 84 degrees F), pH (7.6 – 8.4), and water hardness (12kH to 18kH) are accurate.[3] Also, keep the creatures in tanks of at least five gallons.

To achieve those conditions in my tank, I use the following equipment:

  • To measure the pH, ammonia, nitrates, and nitrites in my tank, I use the API Aquarium Test Kit (link to Amazon). That bundle allows you to make 800 measures, turning it highly cost-effective. It also reveals the parameters incredibly fast.

Snails are tiny, but they won’t appreciate overcrowding. Give them as much space as you can afford. It would help if you also gave them plants like Anubias Barteri and Hornwort. The snails will use them to scavenge for food. Though, you are still expected to feed them. 

Some additional steps that you can take to treat the snails include:

1. Feed Your Snail Properly

A proper diet will aid the snails in their recovery and allow them to grow and maintain their shell. While they can survive on the algae and plant matter (if your tank has enough algae and plant matter), you can use items like lettuce, flakes, and zucchini to supplement their diet.[4]

2. Adjust the Water Calcium & pH

A low pH and calcium content can erode a shell, compromising its integrity and causing its colors to change. You can respond to this development by raising the pH and calcium content.

That objective can be achieved by adding items like crushed seashells and eggshells to the water. You can also buy water conditioners designed to manipulate the pH and calcium content of an aquarium.

The obvious choice on that matter would be the API MARINE CALCIUM Reef Aquarium Calcium Solution (link to Amazon). To use that product, add 5 ml for every 10 gallons. Doing so will efficiently strengthen your snail’s shell.

3. Remove Black Beard Algae

You can combat black beard algae by introducing species that eat it, such as black mollies, platies, and Siamese algae eaters. Yet, you should take each fish’s temperament into account before you add it to the tank. The wrong species may harm your snails.

If you don’t want to add more fish to your tank, you can use chemical products such as Seachem flourish excel and Tetra Algae Control (link to Amazon). You should contact the manufacturer before using a particular product to determine whether or not it is safe for your snails.

If you prefer organic solutions, check the phosphate levels. High phosphate concentrations can encourage the growth of this algae. By eliminating the phosphate in your tank, you can curb the growth of black beard algae.[5]

4. Perform Water Changes

I highly recommend that you perform regular water changes. It isn’t enough to maintain the correct parameters. Water changes remove dangerous components like copper, ammonia, and even phosphates. As a rule of thumb, replace 15 to 20 percent of the water weekly.

Can Snails Change Color?

Snails cannot change color intentionally. However, snails may become lighter when they are exposed to certain external factors. For instance, snails may lose their color due to excessive or insufficient sunlight. Also, in some cases, snails become lighter due to calcium deficiencies.

Calcium plays an essential role in a shell’s development and maintenance. As such, a calcium deficiency can cause the shell to break down. One of the first signs of this deterioration is a loss of color. If the calcium levels are not to blame, you have to consider the pH.

Soft, acidic water will eat into the shell, eroding it and causing it to lose its color. High potassium levels are just as dangerous. In all those cases and more, the discoloration in the shells is caused by an external factor. On its own, the snail cannot choose to change its color.

How do I Know if my Snail is Dying?

The following signs indicate that your snail is dying:

  1. The snail’s shell becomes lighter.
  2. Your snail’s operculum starts to fall off.
  3. The snail’s mantle suddenly collapses.
  4. The snail goes out of its shell.
  5. Your snail shows no interest in food.

When snails are seriously unwell, they will manifest some of the red flags mentioned above. Here is what you should look for:

1. Discoloration

Discolorations can be a sign of ill health. The shell is as important to a snail as any other organ. Therefore, when the snail falls sick, the shell may lose some or all its color. You can expect the same symptoms in snails that are starving and those who have to live in tanks with low water quality.

2. Operculum

The operculum is a plate that covers the shell’s opening. This trap door will remain open once the snail dies.[6] A receding operculum is a sign of sickness in the creatures; the bigger the receding circle, the more serious the illness.

3. Mantle

The mantle looks like a sac. You find it inside the shell. The mantle is not supposed to separate from the shell. When this happens, the mantle collapses. Because it contains organs like the lungs, a collapsed mantle usually leads to death. 

Some snails can survive for days before dying. Some people euthanize snails with collapsed mantles. Others do what they can to make them comfortable before allowing them to die at their own pace.

4. Shell

Have you looked at the health of your snail’s shell? Is it intact? Snails cannot survive outside their shells. If your snail is outside its shell, it is probably going to die. If the shell is broken, the snail is at risk of drying out. It can survive if you act quickly to patch the holes. Otherwise, the chances that it will survive are meager.

5. Appetite

Like most aquatic creatures, snails have to eat to survive. If your snail has refused to eat despite all the food you keep adding to its aquarium, the creature is either seriously sick or injured. If it continues to reject the food, it will eventually die.

6. Listlessness

Snails are not necessarily the fastest creatures. However, they shouldn’t be listless or completely immobile. That is usually a red flag.[7] Therefore, if your snail spends most of its time sitting in a single location, it is most likely unwell.

If you found this article helpful, the following ones may also interest you:


If you notice that your snail is turning black, the first step would be watching the other snails. If only one creature turned black, it is very likely part of its growth. In case the same thing is happening to other snails, test the water parameters.

You should also check other objects in the aquarium, including rocks and substrate. If they have turned black as well, it is most likely due to Black Beard Algae. In this case, you can use algae controllers that quickly get rid of unwanted algae.