Why Is My Parrot Fish Turning Black? (Spots & Patches)

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I was a bit nervous when I saw black spots and patches on my parrot fish’s body. I knew it wasn’t something I could just scrub off and be done with. Luckily, as time passed, I learned why it was happening and how to deal with the issue.

Parrot fish typically develop black patches due to environmental factors, including elevated ammonia, stress, and injuries. These will cause black marks to develop on the parrot fish’s tail, scales, and fins. This is in contrast to black spots, which are usually associated with a parasitic infection.

As we proceed, I will list a few simple steps you should follow to treat both black spots and patches that developed on your parrot fish’s body. For those of you who hurry, the first step would be measuring the water pH, nitrates, and ammonia, using the API FRESHWATER MASTER TEST KIT (link to Amazon).

Why Is My Parrot Fish Turning Black?

Color changes are a cause for concern for many aquarists. Once a fish develops its colors, they expect those colors to remain. As such, when their parrot fish starts turning black, they cannot help but panic.

But that reaction isn’t always called for. Parrot fish can turn black for many reasons, and some of those reasons are perfectly harmless. For instance:

1. Your Parrot Fish Is Merely Getting Older

How old are your parrot fish? It may surprise you to learn that it is perfectly normal for parrot fish to change their colors as they grow.[1] Some fish will lose their color. Others will gain new shades. Young parrot fish may develop black patches, streaks, and blotches, only to lose them down the line.[2]

These changes will keep happening until they mature, at which point their color scheme will stabilize. They may keep the black patches or lose them. At the end of the day, this isn’t an issue.

This explanation applies to black spots as well. Some parrot fish will develop patches, while others will develop spots. It ultimately depends on each creature’s genetic makeup.

2. Black Spot Disease

Some people call this ailment black ich. This is because it causes small black spots to appear all over the fish’s body. Ordinary ich, on the other hand, produces white spots.

Despite the comparison, black spot disease has no connection to ich. Ich is caused by Ichthyophthirius multifiliis.[3] Black spot disease can be traced back to Paravortex turbellaria.

These are flatworms that invade the skin, forming black spots.[4] This makes black spot disease much easier to identify. Because the spots are worms, they do not stay still. Also, like ich, this ailment compels parrot fish to rub against the surfaces in the tank. 

It isn’t as dangerous as ich. Though, a particularly heavy infestation can attack the gills. As the name suggests, black spot disease produces black spots. If your fish has black streaks and patches, you should look for other causes.

3. Your Parrot Fish Was Originally Dyed

Some unscrupulous retailers dye fish to give them rich and vibrant colors that are more likely to attract buyers. You can bury the black marks on a fish by injecting the creature with colored dye.

This can take hours. You have to inject the fish in multiple locations. But those artificial colors will eventually fade, allowing the creature’s dark stripes, streaks, patches, and spots to reappear.

If your fish is mature and you haven’t observed any additional symptoms such as loss of appetite, you must consider the possibility that it was artificially dyed.

Investigate the retailer that sold you the fish. Look for reviews from former clients. If you can find complaints related to artificial dying and drastic color changes, you can conclude that your parrot fish was a victim of the same practice.

4. The Parrot Fish Is Stressed

Many species change color because of stress, and parrot fish are no different in this regard.[5] You cannot identify stress by the nature of the markings on your fish. Some fish may develop spots. Others may develop patches.

The creatures may turn black on the head, belly, or fins. You cannot predict the body part that will change color or the nature of the change. Stress has various causes.

One of the most common is poor water conditions. That includes the wrong pH, temperature, and hardness, not to mention bullying, harsh lighting, and the absence of hiding spots.

It is worth noting that some fish lose color when they are stressed. So don’t expect your parrot fish to turn black whenever they fall prey to stress.

5. Your Parrot Fish Was Damaged

Black patches can appear as a result of skin cell damage. Like stress, various factors can harm your parrot fish, leaving black marks in their wake. That includes infections and injuries resulting from collisions with objects in the tank and violent encounters with larger, more aggressive fish.

A common element that so many amateur aquarists ignore is ammonia. People know that ammonia can ruin a fish’s gills. However, they do not realize that high concentrations can also burn the scales, producing visible marks.

The black marks produced by ammonia, infections, and injuries are rarely organized or symmetrical. You are more likely to see haphazard streaks and patches.

Goldfish knocked against hard surfaces during transit have been known to develop black patches weeks and months later.[6] It wouldn’t be so extraordinary for your parrot fish to suffer a similar fate.

How Do I Treat Black Spots On My Parrot Fish?

As you might have already guessed, treating parrot fish that turn black depends on the cause. As was noted before, some black spots are a sign of trouble. However, others are perfectly innocuous:

1. Eliminating The Parasite

Even though black spot disease isn’t always dangerous, you can’t afford to ignore it. A severe infestation can severely debilitate your fish. Therefore, you are encouraged to place the sick fish in quarantine.

Once it is isolated, you can treat the illness the same way you would a bacterial infection. In many cases, a formalin bath is sufficient. Unfortunately, if you still have worms in the main tank, they will reinfect the parrot fish once it leaves quarantine.

Preventing further infections is difficult. Your best option is to move the fish to a new tank. After a few months, without hosts to invade, the worms in the old tank will die out. If you don’t have any spare tanks, clean the infected tank. 

It isn’t enough to perform water changes. You have to siphon up the organic matter that has accumulated at the bottom. Hyposalinity is another effective option, though this solution isn’t appropriate for tanks with sensitive invertebrates.

Some people have gone so far as to buy fish that eat the worms that cause black spot disease. That includes Yellow Wrasses and Spotted Mandarinfish.

If you feel lost, here is an excellent Youtube video that shows how to cure black spots using commercial products. In that video, the fish owner uses Hikari Prazipro (link to Amazon). Even though I haven’t tried it myself, it does look promising:

2. Improving The Water Quality

Naturally, you have to improve the water quality. A poorly maintained tank will make your parrot fish’s situation even worse. So you have to carry out regular water changes. As a rule of thumb, replace 15 to 20 percent of the water weekly.

I also recommend getting the API FRESHWATER MASTER TEST KIT (link to Amazon). That bundle accurately measures your aquarium’s pH, ammonia, nitrates, and nitrites. I love this kit because it is easy to use and comes with everything you need to do your first tests and analyze the results.

These are the parameters you should aim for:

  • Water pH: 6.5 to 7.0.[7]
  • Ammonia, nitrates, and nitrites: 0 ppm.

The tank also requires a working heater, an effective filter, and air stones to prevent oxygen deficiencies from manifesting. Keep testing strips and thermostats on hand to check the parameters routinely. The ideal temperature for most parrot fish falls between 75 and 85 degrees F. 

And it is also crucial that the temperature remains stable. Frequent fluctuations will stress your fish and perhaps even force it to turn black. That is why I chose the Cobalt Aquatics Neo-Therm Pro Aquarium Heater (link to Amazon), which I also reviewed here.

Don’t forget to match the size of the tank to the number of fish you have. If you want to buy more parrot fish, buy a bigger tank. Overcrowding elevates stress. It also makes tanks more challenging to maintain.

3. Reducing Stress

Parrot fish tanks require plants, which create hiding spots. This is also true for decorations like pots and driftwood. Without these hiding places, stress levels in the tank will skyrocket. Luckily, black spots caused by stress will disappear once the stress levels drop.

Some great examples of plants for parrot fish include Java Fern, Java Moss, and Dwarf Hairgrass. They are very easy to propagate and don’t require any maintenance. You can also place plants like Anubias and Amazon Sword.

However, plants and decorations won’t help your parrot fish unless you remove all the significant sources of stress in their tank. If the water quality is adequate, but your fish are still stressed, consider the location of the tank.

Some aquariums are positioned in areas with a lot of human traffic. Find a quiet location. If that isn’t an option, cover the tank with a sheet. This will eliminate some of the distractions.

I also suggest removing all sources of noise in the vicinity. For example, prohibit your visitors from tapping on the glass. If you can minimize external stimuli, the creatures will recover, and their black spots will fade.

How Do I Treat Parrot Fish With Black Patches?

Like the black spots, your approach to patches, streaks, and blotches will depend on the factors that caused them, for instance:

1. Genetics & Dye

If your fish have a genetic anomaly that has caused them to develop black patches, you can’t do anything to treat them, and you don’t have to because the patches are harmless.[8] Just ensure that your fish swims normally, eats properly, and presents no other worrying signs.

This is also true for fish that have been dyed. Those black marks are the creature’s natural color. You can always dye the fish again to remove them, but the practice is frowned upon. Just let the patches emerge. They won’t harm the parrot fish.

2. Reducing Ammonia

You can combat ammonia by performing water changes. You can also prevent sudden spikes in the concentration of ammonia by removing dead organisms. That includes plants and animals. Otherwise, they will rot, producing more ammonia.

Many aquarists keep water conditioners, such as the well-known Seachem Prime Fresh and Saltwater Conditioner (link to Amazon). The product quickly neutralizes toxins like ammonia. You can use them in emergencies if you cannot perform an immediate water change.

3. Treating & Preventing Injuries

If the black patches on your parrot fish came about due to injuries, you don’t have to take any immediate steps to fix them. Some people are quick to disinfect tanks with injured fish. But in many cases, you just have to keep the water clean.

Perform water changes and maintain the correct parameters. Like humans, fish heal naturally. If the conditions in the tank are conducive, they will recover from their injuries. Give them a clean, well-maintained tank of significant size, and they will do the rest.

4. Dealing With Stress

Like the black spots, you can eliminate patches by treating the stress in your parrot fish. That means adding plants and decorations, removing the aquarium from locations with a lot of human traffic, and eliminating noise sources.

You should also remove large and aggressive fish, especially if they keep bullying the parrot fish. Create a clean, safe, peaceful, and toxin-free environment for your parrot fish.

If you found this article helpful, here are a few others that may also interest you:


As you might have noticed, dealing with your parrot fish’s black patches is pretty as straightforward as dealing with its spots. Moreover, when they appear, the patches don’t always indicate a medical problem.

Symptoms like stress and injuries may be responsible for some of the black marks. Know how to identify them. That will make your job easier when you’re trying to find a cure for the problem.


  1. http://cichlidresearch.com/parrot.html
  2. https://findanyanswer.com/do-parrot-cichlids-change-color
  3. https://www.petcoach.co/article/ich-in-freshwater-fish-causes-treatment-and-prevention/
  4. https://en.wikipedia.org/wiki/Black_spot_disease_(fish)
  5. https://askinglot.com/why-is-my-parrot-fish-losing-its-color
  6. https://animals.mom.com/can-chemicals-cause-goldfish-turn-black-4768.html
  7. https://animals.mom.com/proper-ph-level-for-blood-red-parrotfish-12579301.html
  8. https://aquariumscience.org/index.php/10-10-black-spots/