Why Does My Pleco Have White Patches? (Three Causes)

Have you noticed white patches on your pleco?

It’s sometimes a cause for concern and sometimes is no cause for concern. It all depends on the parameters of your tank.

A pleco can develop white patches for thee main reasons. Those reasons include naturally changing color to camouflage better, an ammonia burn, or a bacterial infection. Two of those causes are concerning while the other is perfectly natural.

This article will help you identify the cause of your pleco’s white patches.

Plecos Naturally Change Color Over Time

Did you know plecos will naturally change color over time. Now, plecos are not like chameleons or octopus. The color change is not an instantaneous one. Instead, the plecos will gradually change color to adapt to the color of the tank.

For instance, if you add a black pleco to a tank with a white bottom, then the pleco will develop white patches as a way to blend in a little better with its surroundings.

You can identify this as the cause if the water parameters in your tank are healthy. The white patches should also be smooth without any fuzziness or anything.

To summarize, a pleco that has smooth white patches in a well-balanced tank that has a white bottom is probably just slowly changing colors to match the rest of the tank.

In other words, it’s not much cause for concern.

Ammonia Burn on Plecos

Ammonia burn occurs when a pleco has too much exposure to ammonia. The result is usually smooth white patches on the pleco.

The difference between ammonia burn and a pleco naturally changing color can be difficult to spot.

The best way to spot ammonia is to take a water sample in your tank. If your tank has a high amount of ammonia, then your pleco probably has an ammonia burn.

Treating a fish with ammonia is not difficult. The first thing you need to do is get your ammonia levels under control. A better filtration system is often the best step.

Another good idea is to place the pleco in a quarantine tank and treat it with medicine. My recommendation is a medicine called Furan 2 and Kannaplex in the tank for as long as the pleco has the white patches. This will make the tank a little cloudy, but if you keep the ammonia and nitrite levels down, then your pleco should recover rather quickly.

On a related note, you may also have too much waste in your fish tank if the ammonia is too high. This can cause holes to form in the dorsal fin of your pleco.

White Patches from Fungal Infection

Does your pleco have white patches that appear a little fuzzy?

If the white patches appear fuzzy, then the pleco almost certainly has a fungal infection.

This is most often caused by some sort of damage the pleco received to their skin. Two common causes can be an attack from another pleco or a burn from the heater.

It’s actually quite common for a pleco to get stuck behind the heater and receive a burn. The fungus will then grow on the dead skin.

Again, you should immediately place the pleco in a quarantine tank. This time you should add an antifungal medicine called Pimafix (commisions earned on this link see: Affiliate Disclosure) to the tank until the pleco heals.

You should expect it take about a week for the fish to fully heal.


That covers it for the three main causes of white patches on a pleco. Two are cause for concern, but the remedy is thankfully extremely easy. The other cause of these white patches is a perfectly natural one that is actually kind of cool.

2 thoughts on “Why Does My Pleco Have White Patches? (Three Causes)”

  1. I have a large pleco in a 20 gallon tank I changed the filter and in 3 days it’s already dirty now it has a very large hole above its Gill under its eye and it’s white.Imagitarium is what I’m going to first attempt but it does say to move out the carbon and the carbon in the filter are together any suggestions?

    • It sounds like some sort of fungal fin rot. That usually means the tank has too much waste in it.

      As for the carbon, you don’t need carbon in the filter. That’s really only necessary after putting medicine in the water in order to clear it out. Sponges work fine as a filter.


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