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Dust-Like Particles in Aquarium (How to Fix)

Nothing ruins the viewing pleasure of an aquarium more than water that has something floating around in it other than fish. There are many different things that could be floating in fish tank water that look like dust particles. You might even see coloring such as yellow or green showing up in the water. But what are those dust-like particles floating throughout your tank?

Dust-like particles in an aquarium can be caused by different things including a recent substrate vacuuming, aquarium water that’s not cycled properly, a filter full of organic compounds, decaying fish and/or plants, a filter that’s too small for the tank, bacterial bloom, and bugs like ostracods or scuds. 

There could be other reasons you have what looks like dust in your aquarium water and I’ll try to cover everything I can think of in this article. Sometimes when you think you have everything running smoothly and find out that it’s not, there’s just one little tweak you need to do to get back on track with a healthy tank.

Let’s begin…

What Causes Dust-Like Particles in an Aquarium?

Firstly, let me just say that I feel the same way. I don’t like anything floating in my water other than the pet fish I bring home to take care of.

Here are some different things that can cause dust like particles in your tank.


  • A recent aquarium cleaning can give off the effect of dust-like particles in the water. That’s because there’s debris floating around that got rustled up from being embedded in the substrate when you were running your water vacuum through it.


  • Now this might appear to be an obvious one for an experienced hobbyist however, someone new to fish keeping might be wondering if this is normal and if its a potential problem with the tank.


  • The answer is it’s absolutely normal, and you don’t have anything to be concerned with if the dust showed up right after a water change. If it doesn’t go away after a few hours, then you might have an issue and I recommend you keep reading.


  • If the aquarium water is not fully cycled, it’ll often look cloudy and almost like there’s dust floating in the tank. If you’re new to the hobby and need to learn about the nitrogen cycle, you can read my article on that topic here.
    • It’s also possible that an older tank would be thrown into the nitrogen cycle if too much water was taken out in a water change in combination with bacteria being sucked out of the substrate and cleaned out of the filter media.


  • If an aquarium filter is overrun with organic compounds, they can run back out of the filter into the water causing a dust-like appearance.


  • Decaying fish and plants left untouched on and in the substrate can start to break down and float around in the tank.


  • If the filter is just too small for the size of the tank, you could have organic compounds floating right through the filter, never really being captured. Or the tank is so big and the filter is too small that a lot of the water just isn’t being filtered properly.


  • A bacterial bloom can look just like dust particles in the water. If the coloring of the water changes, then I can almost guarantee that’s what you have going on in your tank. Sometimes however, the dust (bacterial bloom) in the water will still look white or gray.


  • Bugs in the fish tank can look a lot like dust particles floating around. I know from experience as I have dealt with scuds in my 10-gallon tank. Most tiny bugs will look like dust particles floating in the water as the bugs swim about. To know for sure, you’ll have to get ‘up close and personal’ and really have a good long look.

clean aquarium

How to Fix Dust Particles in Your Aquarium

Now that we have identified numerous ways your fish tank could appear to have dust particles floating around in it, let’s look at how to fix each of these issues.


  • If the dust is happening because of a recent water change, then there isn’t anything for you to do other than wait for your filtration system to clean out what it can. The filter won’t grab everything floating as some bits of debris will just float to the bottom of the tank and once again vanish into the substrate.


  • If by chance your water stays cloudy, then I would have a look at all of my recommendations below.


  • Aquarium not cycled or knocked back into a cycle. If you are not an experienced fish tank owner, you really should take it upon yourself to learn what the nitrogen cycle is and what affects your water parameters.


  • If your aquarium isn’t cycled or you unknowingly knocked your tank back into the nitrogen cycle, here are a couple of things you can do to help save the fish.


  • Use a biological enhancer immediately. Biological enhancers will put your water into a temporary cycled state. It’ll add beneficial bacteria and get rid of ammonia and nitrites. Use the maximum amount the label says for your size of tank.


  • If you have access to a sponge from a filter in a cycled healthy tank, then get that and put it in your tank immediately. This will offer beneficial bacteria which will start working on cycling the water right away.


  • Perform a water change every few days until you notice a difference in the look of the water. You want the cloudy, dusty look to dissipate.


  • If your aquarium filter is overrun with organic compounds, chances are it won’t be able to hold everything in the filter. This means you’re going to see a lot of debris and dust-like objects floating around.
    • To remedy this, regular filter maintenance is recommended. Keeping up a regular schedule with all fish tank maintenance is “the” way to keep a healthy tank.
    • Sometimes a filter gets bunged up quicker than usual if you’ve been overfeeding and the fish are pooping more or if you have live plants and there are a lot of dead leaves decaying.
    • In general, with all things being the same such as feeding amounts, your filter maintenance can be done on a set schedule.


  • Decaying fish and plants means decomposing materials can potentially be floating in the water column before being picked up by your filter. Keep on top of dead fish and pieces of plants that break loose. Scoop these things out of the tank once spotted.


  • If the filter is just too small for the tank, it can’t filter enough water to make a difference. Sure, it will do some filtering and is better than not having a filter at all, but it’s not enough.


  • You should get a filter that is rated to handle the size of your tank and up to 10-gallons more. Getting a filter that is just big enough is only okay if you’re keeping a minimal amount of fish in the tank and you are very careful with how much food you give them.


  • A bacterial bloom. Out of all the issues presented so far, aside from the uncycled tank, this one can turn into a real problem. It’s not uncommon for fish tank owners to run into an algae bloom at one time or another. Water-borne algae blooms are different than regular algae that grows on something in the tank.
    • A water-borne algae bloom floats in the water. It colors the water and can be a cloudy white, green, and even yellow hue. It’ll definitely look like dust particles in the aquarium.
    • You could do a large water change and use a water treatment for algae and or you could invest in a UV sterilizer. I always recommend these units, especially if you don’t quarantine new fish and plants.
    • UV sterilizers draw water into the body of the filter where a UV light zaps the water, killing any water-borne algae. I have a full article on the topic that you can find here.

To purchase a UV sterilizer, check these ones out on Amazon.


  • Bugs in the fish tank can be another reason it looks like you have dust in the tank. I know because I have had issues with scuds. I also know that ostracods are quite common in a lot of tanks.
    • It’s not that people want them, it’s because they get transported by purchasing fish or plants and not quarantining them.
    • Aside from taking everything out of the tank and starting over, the best way to fight these little critters is to cut feeding way back and vacuum substrate once to twice a week until you don’t notice them anymore.
    • Scuds and ostracods are not going to cause the fish or plants any problems. When these little guys are thriving in your tank, it just means you have a healthy environment with maybe a wee bit too much excess food.

More Ways to Clear Dust Particles Out of the Aquarium Water

There are other things you can do to help clear particles out of the fish tank that I hadn’t mentioned above but can be an important way for you to keep crystal clear water.

Have you ever heard of a flocculant? A flocculant is a substance that when added to water will cause small particles to clump together. When the particles are not clumped together, they might not be big enough to be picked up by your filter.

When you add the flocculant like this one from Amazon, it causes the small particles to clump which then become large enough for your filter sponge to pick up.

Another method to catch those really small particles is to add what is called filter floss (also called a polishing pad) to the filter media. These dual density filter pads can be cut to fit any size filter and will definitely help clean up your water.

Here are some options for you on Amazon for filter floss.


To conclude this article, I want to point out the obvious takeaways for me and should be important to you.

Ensuring your tank has gone through the nitrogen cycle is extremely important for the fish so they aren’t dying in toxic water.

Regular maintenance is extremely important. Consistency with maintenance week after week throughout the year (and over the years) will promote a healthy tank and I guarantee less problems will pop up.

And lastly, sometimes when we look at our tanks and the water is hazy, it’s because a biofilm has accumulated on the glass which makes it appear like there’s dust in the water. If you were to clean your tank’s glass or acrylic twice a week, you could avoid mistaking this issue for poor water quality.

I hope I was able to provide you with some valuable information in your quest to fix what looks like dust particles in your aquarium. Thanks for reading. Good luck!

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