Updated at: 23-06-2022 - By: Helen Skeates

A common problem in fish tanks is algae and excrement buildup, so if your issue is how to get rid of mold in fish tank, you aren’t alone in your worries. When it comes to aquariums and tanks, your primary focus is likely to be below the water’s surface.

There are many things to keep an eye out for when cleaning your tank’s green filter. In addition, molds and other fungal infections may occur at the same time.

Infestations, whether they’re on the surface, within, above, or below the surface of your tank, must be eliminated.

Unless you’ve been working with fish tanks and aquariums for a long time, you know how difficult it is to clean them after an infestation. For the time being, let’s concentrate on mold removal.

Steps On Cleaning Molds On A Fish Tank

Since fish live in a confined area, they are distinct from dogs and cats in terms of the care they require, whether it’s one or a complete school. Here are some things you can do if molds have infiltrated their space.

Mold In The Fish Tank: How To Remove It - FishLab

Step #1. Prep a temporary tank for the residents

This step is crucial, because your fish will need a temporary home until their own tank is cleaned and ready for them to move back in. Leaving your pet unattended in the open or in an environment that isn’t appropriate for them is a recipe for disaster.

If you’re using tap water, let the container sit with the water from the original tank for about a day after locating an appropriate container. This is due to the fact that you’ll need to allow the gas and chlorine to dissipate before putting the fish in.

As a last resort, you can always utilize water from your own tank to ensure that the water is safe. Chlorine can take up to a week to evaporate in extremely concentrated water, but you can also have your tap water tested right away.

Step #2. Drain the tank content

You can now begin the process of emptying the tank of concern once the fish have been transferred. Some tanks have built-in drains, but this is not the case for the majority of them, which must be emptied by hand.

Grab a bucket or something similar that will fit through the tank’s opening, but leave some room to spare so that you don’t damage anything. If you don’t want the molds to return, you’ll need to remove all of the water from the tank.

Step #3. Remove all the ornaments and other tank content

Following the removal of all the water, you must also remove all the plants, driftwoods, filters, and decorations that you have placed in the tank. Everything that has had touch with tank water should be assumed to have mold spores and should be cleaned if you wish to avoid the molds returning.

Step #4. Clean all the tank content

Now that you’ve removed the fish, you can thoroughly clean the tank you intend to return. Use water and a toothbrush to clean all the surfaces, getting rid of any dirt or algae that may have accumulated.

If you don’t know how to properly use items like soap or bleach, we advise you not to use them, simply in case you can’t thoroughly rinse them. Also, be careful to scrub and scrape the tank’s glass exterior and interior.

Step #5. Rinse, sterilize and return the tank

After brushing everything, rinse them in clean tap water to remove any mold and other debris that may have accumulated. Use a sponge to remove any stains that may be clinging to the tank’s glass.

Pour boiling water over the tank and its contents to sanitize them, especially if mold and spores are still present. Living plants require a gentle touch and plenty of rinsing to remove the white mold that develops on them.

Once you’ve rearranged the tank to your liking, go ahead and fill it up with tap water. Allow at least 24 hours for the water to return to normal before reintroducing the fish.

Fish Tank Maintenance Tips

  • To avoid the growth of mold, you should remove around 10% of the water from your aquarium each week.
  • Overfeeding will lead to a buildup of food in the tank, which will hasten the growth of mold.
  • When cleaning a tank, don’t forget to clean the lids, where airborne molds tend to attach.

a little extra help

If you want to keep your fish tank free of mildew and algae, consider adding suckerfish and snails. As for snails, they like an aquarium filled with freshwater. Suckfish on the other hand prefer tropical aquariums.

Fish Tank Mold Types

You may see green fungus, black fungus, black beard algae, white fungus, and algae in your fish tank.

1. Green fungus

When the tank’s water quality is inadequate, the green fungus appears. Green fungus thrives in nutrient deficit.


Give your fish a variety of nutrients to eat. To avoid the growth of mold in your tank, you should replenish the water every three days.

2. Black fungus

A surplus of leftover food is what’s causing the black fungus to grow on your aquarium’s surface. In some cases, elevated phosphate levels are also a trigger for the growth of black fungus.


Remove the toxins from your tank by flushing it out. Monitor the water’s phosphate content.

3. Black beard algae

Black beard algae, sometimes known as red algae, are a type of algae that grows on the skin. Phosphate levels in the algae have grown.


The tank needs to be refilled with a fresh supply of water. Clean the tank’s siphon and treat the water that has just been added.

4. White fungi

Low-quality water causes the growth of white fungus. The open wound on your fish is also a factor in their look. Injuries and skin fragments that float in the water provide food for the fungi.


It’s important to flush the tank with fresh water and eliminate any floating food. To prevent the growth of white fungus, clean your fish’s wounds and wrap the diseased region.

5. Algae

Water, nutrients, and light all contribute to the growth of algae in your fish tank.


Try adding fish that eat algae to your tank. You should avoid exposing your tank to direct sunlight at all costs. Try to keep artificial lighting in your aquarium.

aquarium - How to remove mold/algae from the stones in a fish tank? - Pets Stack Exchange

Reasons Behind The Growth Of Mold In Your Aquarium

Mold can grow in a fish tank for a variety of reasons, including dirty water and nutrient imbalances.

If you have a problem with mold in your aquarium, these are a few of the most prevalent causes.

1. Extra feed

Overfeeding is a common practice among fish keepers who care about the well-being of their aquatic pets. As much as possible, the fish take as much as they can, and the rest is deposited to the bottom of the tank.

Mold forms as a result of the phosphorus fumes produced by the leftover food that is gathered at the end. The fish are also harmed by these toxic vapors.

2. Décor

Make your fish happy by putting brightly colored ornamental things in the tank, but be careful if you have live plants in the aquarium.

In order to keep fish tanks healthy, plants need to be replaced on a regular basis. It takes a very long time for the plant to begin the process of oxygenation when it is dying.

At this point, the tank’s atmosphere is such that the tank’s corners and surface regions are covered in black or brown mold. Molds thrive on ammonia, which is boosted by the presence of these toxic compounds.

3. Light

It’s no secret that fungi thrive in the presence of sunshine. Algae and mold thrive in warm, humid environments, such as those created by an aquarium placed in direct sunlight.

The generation takes place at the tank’s top corners. This can be avoided by keeping the tank out of direct sunlight and using artificial lighting.

4. Cloudy water

The faeces, food particles, and other material in the water tank will cause the tank to appear foggy if you do not clean it.

Mold thrives in this type of environment, and it proliferates as a result. In some cases, it may be necessary to completely replace the tank due to the presence of mold.

So cleaning before the situation worsens is the most sensible course of action.

5. Delayed changing water

A buildup of nitrates in the tank is a sure sign that you haven’t changed the water in it recently. Algae thrives on nitrates, which are present in high concentrations in the water.

White mold in fish Tank-Let’s get the job done

Health of any aquatic animal is directly related to the quality of the water in which they are housed. Poor cleanliness in fish tanks is caused by the growth of mold, a fungus. Aquarists face a common problem: the growth of fungus in their fish tanks and aquariums. Fish keepers need to know how to remove mold from their tanks.

Natural processes are the most straightforward explanation for this. Other microbes can flourish in water that is rich in organic food, minerals, vitamins, and leaves. It’s natural for white or green mold and algae to reproduce in this situation because they have all the materials to do so.

How does your fish tank grow mold?

There is no denying that we often do not take into account how much food we are feeding to our fish. Overfeeding is a way for fish keepers to interact with their animals. Uneaten food accumulates in the tank’s bottom and degrades the water’s quality when the fish cannot consume it.

Further, the ph of the water will be lowered and the organic foods, vitamins, and nutrients will be broken down into compounds like ammonia, nitrate, etc.

Aside from encouraging the growth of germs and mold, these chemicals can also affect fish skin and growth.

Furthermore, the tank already contains wood, plants, dead fish, and fish feces that produces underwater mold as a carbohydrate supply. There are both useful and non-beneficial germs, microbes and other living water-borne objects that are created when they degrade.

Is mold in aquarium visible?

When the glass in your aquarium is thoroughly cleaned, you can see the white mold that is forming inside. In the aquarium, it can be seen growing on just about anything. Everywhere you look, this white fuzzy mold can be found lurking. Like a canvas on the boat, it will appear in the water as fibers.

This is something that can be seen in both small and large tanks. A gloomy fungus colony can be formed by airborne mold spores that are not visible to the naked eye. Because of a variety of internal and environmental factors, fish are frequently afflicted with fungus.

How dangerous is mold for fish tank?

White mold can be harmful to humans, but you shouldn’t worry too much about it if you keep fish. Mould, for example, is an useful microorganism until it pollutes or degrades the water quality. To avoid blurring the water in the tank, we always advise not allowing it to grow too large.

How to prevent mold growing in Fish Tank?

When a fresh organic material, such as driftwood or anything that releases carbohydrate, is added to a fish tank, it is likely to form mold. This type of issue can be easily remedied by performing a routine cleanup. As long as other aquaponics systems like pH level, nitrate, and water quality are in balance, white fungus (mold) poses no risk to fish.

  • It’s recommended that you perform a weekly water change of 30-40 percent of the fish tank’s total volume.
  • Check to see if the filter has to be cleaned or replaced on a regular basis.
  • When setting up an aquarium for fish, use sand as a substrate.

FAQs About Mold In Fish Tank

Can mold in fish tank kill fish?

Mold can, in fact, be fatal to fish. Changing the ph of water can disrupt the water’s healthy balance, which is what this does.

Is mold bad for fish?

The amount of mold in the water will have an effect on the outcome. If the growth of mold is minimal and disappears after a day or two, the situation is good; however, if the mold persists for an extended period of time without disappearing on its own, it will colonize the tank and have a detrimental effect on the fish.

Why does my fish tank have white mold?

Fish tanks can become infested with mold for a variety of causes, and it’s a normal and inevitable part of life. Mold can grow in aquariums that are properly cared for.

Can i use vinegar in fish tanks to clean mold?

Vinegar can be used to remove tough algae and mold from the fish tank. It’s important to rinse thoroughly after using vinegar to remove all traces of it, however excessive amounts aren’t recommended.

how to remove mold from a fish tank


A clean tank needs that you know how to remove mold from a fish tank, and then how to return it. In order to prevent the growth of molds, you should inspect and clean your tank on a regular basis.