How To Remove Mold From Fish Tank-Step By Step

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

The healthiness of any aquatic vertebrate living in an aquarium or tank depends on the cleanliness/purity of the water they living in. Mold-a fungus, is often found growing in fish tanks, is responsible for poor hygiene of fishes. Fungus growing in fish tanks or aquarium is a common issue for aquarists. So, how to clean mold from fish tank is a must-know for fish keepers.

Nature doing its natural work is the simplest explanation for this. When the water is rich in organic food, micronutrients, vitamins and leaves, it can grow other microorganisms. White or green mold, algae is easy to grow as they have all the ingredients to root, so reproduction is its natural phenomena in this condition.

How to clean mold from fish tank
White mold In Fish Tank

How does your fish tank grow mold?

We have to admit that, most of the time we don’t calculate how much food we are feeding to fishes. To make a connection with them overfeeding becomes a habitat for fish keepers. When the fishes can’t eat those foods, uneaten food then sediments in the bottom of the tank and make the water quality poor.


This will further result in lowering the ph of water and disintegrating the organic foods, vitamins into chemicals like ammonia, nitrate etc.


These chemicals will not only help to grow bacteria and mold but damage fish skin and harmful to fish growth also.


Moreover, there is already wood, plants, dead fish, fish poop which breeds underwater mold inside the tank as a source of carbohydrate. All these decompose create both beneficial and non-beneficial germs, microbial and other living water-borne subjects.

Is mold in aquarium visible?

If your aquarium glass is properly cleaned, you can observe the white mold growing inside. It grows on almost everything in the aquarium. From guppy grass to rock and décor wood, this white fuzzy mold can be seen anywhere. If it grows big, it will look like fiber floating in the water like a canvas on the boat.


This thing is visible both in small and big tanks. Sometimes unseen airborne mold spores can create a colony of gloomy fungus. Fishes are often found infected by fungus infection due to many other internal and external reasons.

How dangerous is mold for fish tank?

White mold is dangerous but for fish this isn’t something that you should get too much concern about. There are many beneficial microorganisms naturally grow in the tank, mold is one of them until it makes the water dirt or unhygienic. But we always recommend not to let it grow that much, that it makes the water blur inside of the tank.

Clean mold from Fish Tank –The right way

Regular cleanup is a mandatory task for aquarium owners, and cleaning mold from it does not take any special effort. There are some dos and don’ts to follow to ensure a proper cleansing and prolonged tank life. Things to buy:

Method 1: Back To the Drawing Board

This method is a complete cleanup process to eliminate all kinds of mold, moss, algae, dirt whatever kind of impurity that deteriorates the water condition. These items will be required to kick off:

  • Scrubber/ scouring pad made of nylon, not the steel ones
  • Mask
  • Hand gloves
  • siphon/vacuum
  • small toothbrush
  • Fishnet
  • Small container with fresh water to keep the fish for some time.
  • Razorblade
  • Water testing kit


Step 1. Transferring the fishes


Turn off the filter and take an old container (must be clean) and transfer the fishes into that with the help of a fishnet. Make sure the water temperature is the same as the current tank, and it is not direct tap water rather filtered and conditioned properly. Transfer the gravels and pebbles to store the useful bacteria in new condition and make it more suitable for the fishes. Use hand gloves and mask from the very beginning to avoid inhale and contact with mold spores.


Step 2. Changing the water


Use a hand pump to take out the water. If the tank is big, you can use an electrical siphon to do it quickly.

Step 3: Cleaning the Tank lid

The tank lid can get moldy and work like a fungi or algae source if not cleaned regularly. To clean the lid, it need to be taken off and cleaned with hot water to get the loose particles of the cover. Then scrub it inside & outside with a scrubber and normal detergent. If there are heavy algae on it, use a razor blade with caution. Don’t make any scratch on it.

Rinse it properly, get all the carp out of lid and covers like its nothing. After they soak, put them back where it fits.


Step 4. Getting rid of mold


In this step, with the help of scrubber or scouring pad (made of nylon) scrub inside out, top to bottom and get rid of all kinds of dirt that are lingering in the tank. You can use a small amount of vinegar as a disinfectant, but the amount should be as less as possible. While scrubbing from one portion to another, make sure to rinse every portion thoroughly. No smell of vinegar should be leftover. You can use hot water also.


Step 5. Rinsing properly


Rinse the tank 2-3 times after scrubbing, ensuring a crystal clear fish tank with no leftovers of gunk or any dirt. If Possible, let it soak for some time in the sunlight.

Step 6. Ensuring proper return


Finally, before putting the fishes back to their cleaned tank, make sure the temp of the new water is the same as old container, and filtered water is being used. Get the gavels back and make some natural décor with driftwood and other materials locally available in pet stores. Get a water treatment conditioner to dechlorinate the tap water.

Method 2. Clean The Infected Substances

This process involves 40% change of water and removing the white fuzzy mold by only cleaning up the materials on which it sets on. Mostly the driftwoods get this gelatin substance more than anything else as it produces carbohydrates for the mold. 

  • Take the driftwood out of the tank.
  • Wear hand gloves and clean it properly
  • Let it soak in sunlight for an hour or two
  • Put it back in the tank again
  • Find if the fungus has grown on any other thing like gravels etc. and repeat the same process
  • Change the water like 40% to ensure a cleaner environment

Method 3. Let Sucker fish, snail, pecos Eat it

This a natural method to remove mold from any fish tank or aquarium. It involves putting some snails or Pecos or shrimps into the tank.

  • These aquatic mammals love fungus and gobble it as food.
  • You can keep any of these along with other fishes also, or just when mold shows up.
  • It takes 1-2 days to eat those white mold, all over the tanks.
  • As, the Pecos has eaten the mold, in a very quick time, you may see excess poops for this on the substrate.

How to prevent mold growing in Fish Tank?

Fish tanks usually grow mold, whenever something new organic is added to the tank, especially driftwood or anything that releases carbohydrate. Regular cleanup is a simple solution for this kind of problems. Besides that, mold or white fungus is not that harmful to the fishes as long as other aquaponics systems like ph level, nitrate, water condition are in a balanced state.

  • Changing 30-40% of fish tank water weekly is considered to be good.
  • Clean the filter once in a while and check if it is working properly.
  • Add some sand as a substrate to make it natural to the fishes.
  • Use water treatment conditioner whenever changing the water.

Final Words:

Hopefully, you will not get panic seeing white mold in your fish tank and mold in a fish tank will not be a big problem anymore, as you know to tackle it by this article. This is a natural process to grow it in tanks and many fish keepers even not bothered to remove it because they know it will eventually die in when the organic materials stop to release carbohydrate. So, you now should have an idea of how to clean mold from fish tank.

FAQs About Mold In Fish Tank

Can mold in fish tank kill fish?

Yes, mold can kill fish. What it does is, it affects the ph of water and any significant change of ph can disrupt the healthy balance of the water.

Is mold bad for fish?

It depends how much mold has got in the water. If mold growth is less and vanishes within a day or two then its fine, but if mold is persisting for long time and not going naturally, then it will colonize the tank and leave a very bad effect on fishes.

Why does my fish tank have white mold?

Fish tank can grow mold for various reasons and it’s a common and natural phenomenon. Properly maintained aquariums can also grow mold.

Can i use vinegar in fish tanks to clean mold?

Vinegar can be used to clean stubborn mold or algae sitting in the fish tank. However too much vinegar is not recommend and after introducing vinegar proper rinsing is must to completely remove any dent of it.

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