White slimeWhite slime in fish tank is actually the growth of white-colored algae. This common tank algae is not particularly dangerous for your fish, but they develop and spread very quickly.

There are many ways to get rid of them and also prevent them in the future. Keep reading as in this article, we will discuss the aspects.

What Causes White Slime in Fish Tanks?

Several factors can contribute to the build-up of the white slimy stuff in fish tank. Some of these causes are natural and cannot be prevented entirely, while others can be avoided easily. Let’s take a look:

– Bad Water Circulation

This is something that mostly happens in a new tank. While doing the setup, you may have chosen the wrong filter. It could also be because the filter has stopped functioning for some reason. This calls for inadequate water circulation in the tank. As a result, the white algae cannot get washed away, and thus it starts to build up in different places.

– Overfeeding

A very common cause of the development of white slime inside the fish tank is overfeeding. The latter may happen if you are a fair beginner fish owner. You might think that giving your fish more and more food is good for their growth, but that’s not the case.

Fish have a limited capability for the amount of food they can eat. After that limit is reached, they will stop eating. If you’ve given them more food than what they can take, the uneaten food remains in the water. The food will then gradually break down and become a source of food for the white algae.

– Too Much Lighting

One of the key reasons why algae start growing in a tank is that they get an abundant amount of light. You are probably keeping the light of the tank on all day, or you are keeping it on for longer than necessary. It could also be that the intensity of light is too much, although the timing is fine.

If the case doesn’t have to do with keeping light on the tank, then natural daylight could be the cause. Hence, your fish tank is placed in a spot that gets direct sunlight, it can promote algae growth, and the longer they get the light, the more they will continue to grow.

– Sugar Build-up

The aquarium might have a source of sugar, and the reason behind that could be the plants inside the tank—especially driftwood from pine or another tree containing large amounts of sap. This is a less common but equally probable cause of noticing white mold in fish tank.

If you’re using a DIY carbon dioxide system, then it’s also possible. Additionally, if you have a decoration that is not intended for aquarium use. Furthermore, some kind of residual medications still floating in the water, as all are potential contributors to white slime.

– Overcrowded Tank

If there are too many things in your tank, white slime may build up in it, because the filtration will have a hard time clearing it up. It could be that it’s stuffed with decorations or that there are way too many fish in there. If the size of the tank is small, it only adds to the problem.

How To Get Rid of White Slime ?

Here are some ways you can free your tank from the invasion of white algae:

– Clean the Tank Thoroughly

Even without having a white slime issue, it’s important to keep the tank clean. You should keep a watch on the tank on a regular basis, and whenever you notice any type of clear slime in fish tank, it’s best to wipe it off as soon as possible. The longer you leave them be, the more they will develop and spread.

Make sure to check the nooks and corners properly, since algae might build upon the rocks, the decorations, or even the sides of the tank. If necessary, take all the contents of the tank out and clean them one by one. If there are any dead plants or dead fish, remove them immediately.

You can use an aquarium brush or a regular household sponge for cleaning. If it’s a household sponge, don’t use it for anything other than cleaning the aquarium slime, since any cleaner or chemical is not recommended as they may harm your fish.

– More Frequent Water Changes

If you have noticed white slime in the tank, it’s best to notch up the number of times you change the water, especially if there is too much of it everywhere.

This is to prevent further growth of algae in the tank. Even after cleaning the white slime, there might still be more residue foods or medications, and these may just contribute to building it again. Some foods and waste materials even remain in a dissolved condition, which is what the algae prefer.

Ideally, the water change should be done weekly, however, in this case, you can do it every other day for at least the first couple of weeks. If the case is too bad, it is recommended to do it every day until it becomes fully clean. Replace the aquarium water with fresh, chemical-free water.

Keep in mind:

Do at least 25 to 30 percent of water change to reduce the amount of fuzz food in the aquarium. If you’re changing the water daily, keep it at 20 percent. Don’t change the entire aquarium water at once since it will be difficult to create the exact tank conditions again.

When doing the water change, make sure that there is no change in the water conditions. All the parameters should remain the same. You can use a testing kit to ensure that. This is important not only for the well-being of the tank population but also to prevent the growth of more algae.

– Introduce New Members to Your Tank

Do you want to keep away the white slime in aquarium in a more natural process? Well then, time to put some algae eaters in the tank. They will successfully prevent more algae invasions in the future. On top of that, more life and diversity will be added to your tank.

On another note, algae-eating fish can help keep your tank clean, such as snails and hermit crabs. Since both of them feed on algae, they can effectively maintain a clean tank.

Keep in mind that they cannot clean off the slime that is currently in the tank, hence you can put them after you have cleaned the tank yourself. Therefore, you won’t have to go through this kind of trouble again.

Whichever fish, snail, or shrimp you decide to add to the tank, do proper research on the species. They might not be compatible with the fish on your tank, or they might require different water conditions and care. Only choose the ones that are compatible with the aquarium in question.

However, on a more general scale, here are some algae eaters that are best for white algae-

  • Barbs
  • Mollies
  • Siamese algae eaters
  • American Flagship
  • Danios
  • Chinese algae eaters
  • Sun snails
  • Nerite snails

You can choose whichever of these match the requirements of your tank.

– Manage the Lighting

Lighting is one of the biggest reasons for white algae growth, you will be surprised at how easy it is to prevent white algae or any other type of algae from appearing in the tank.

Basically, nine hours of light is more than enough for a fish tank, although some have special requirements and need more light. If you have any such fish in your tank, then you can keep the light on all day, however, you should still go and turn off the light for a while every few hours.

Daylight can also cause the growth of white slime, if your tank is located near a window, you can move it to a different place. Nevertheless, if you can’t do that, consider putting up curtains so that you can control the amount of sunlight it receives.

You can also introduce more plants into your aquarium, and they will provide more shade to the place and also use a part of the light themselves. Just make sure the plants are adapted to your aquarium environment and population. Furthermore, you should quarantine them first in case they are contaminated.

– Don’t Overfeed

This is very important not only to keep away the white algae but also for the health of your aquarium population. It is important to know that overfeeding can cause your fish and other aquatic animals in the tank to get sick. The latter will cause the parameters of the water to change, and it will also pollute the tank as it creates more waste, as a result, algae will start to grow.

Keep in mind that every fish has different capacities, hence you should be mindful about how much food you should give. It is better to give less food to your fish than more since fish can survive just fine on a small diet.

Don’t give more than what the fish can finish in a couple of minutes. After the first few minutes, they usually won’t touch the food for the time being.

– Maintain Your Aquarium Filter

The reason why it’s difficult to prevent the growth of white algae sometimes is that the filter of your aquarium can wear off. It will appear to work just fine, so you won’t even realize it’s not doing its job until you start seeing those white slime everywhere.

It’s not only the filter as it can also be the heater, which may be damaged and makes the water warmer than usual, thus promoting algae growth. It can be your fault, too if you are careless about filtering tap water before adding it to the tank.

Either way, you should check for any kind of change to the routine of the aquarium environment if you see white slime growing, there might even be white slime on aquarium filter. Upgrade the tank’s water pump to have a high-quality filter. Moreover, it will help you have a regular water cycle and increase the speed to flow as well.

A mechanical filtration system will be even better, it might be expensive, but it’s an investment worth making. You will encounter the problem much less often with a long-lasting, expensive filter. The members of the aquarium will also appreciate this.

– Use Chemicals

This is something you should do as a last resort, hence if the case of white algae is a tough one and there is a heavy accumulation of it everywhere, which is difficult to get rid of by the above methods, you may use chemicals.

Only use chemicals that are aquarium friendly. Make sure to do your research properly. There are chemicals that affect all types of fish, while other chemicals that only affect certain ones. You don’t want your fish to die, after all.

White slimeHow Much Time Will It Take To Get Rid of IT?

Now that all has been said and done, you might be wondering how long you will have to keep doing this. Sadly, it’s quite difficult to get rid of white algae in aquarium immediately, and they are hard to control, so you will have to have patience.

It’s hard to predict the exam amount of time it will require, although it mainly depends on how early you start working on it, how you maintain the tank, and how bad the invasion is.

In a general sense, you should remain prepared for a few weeks of maintenance, nevertheless sometimes it only takes a few weeks, and other times it may take months. That’s why it’s recommended to try to prevent it from happening in the first place.


Now you’re ready to start working on the white slime in your fish tank. Let’s take a look at all the crucial points you need to keep in mind once again-

  • Keep the aquarium light on for not more than nine hours daily, or at least turn it off every few hours before turning it back on.
  • Do 20 to 30 percent water changes every other day for a few weeks until the algae reduce.
  • If you keep the tank near a window, use blinds or install more plants. Only use aquarium-friendly chemicals if other methods don’t work.
  • The sponge you use for cleaning the algae should be new and should not be used for any other purpose afterward.
  • Before adding algae eaters to the tank, check their compatibility with the water parameters and tank mates. 

White algae can be a very troublesome issue to deal with. But if you follow all the preventive measures mentioned in this article, hopefully, you won’t have to deal with it ever again!

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