Get Rid of Cloudy Aquarium Water Once and For All


Nothing is worse than spending your hard earned money on a fish tank for your family to enjoy, only for it to be constantly murky and downright unattractive. Cloudy water is not an insurmountable problem. I can tell you how to eliminate your cloudy water once and for all.

First you must determine what is causing your water to be cloudy.

There are three main types of cloudiness in your water:

  1. Free-Floating Particles (Part I)
  2. Bacterial Bloom (New Tank Syndrome) (Part II)
  3. Green Water (Free-Floating Algae) (Part III)

Part I : Free-Floating Particles


You have just added new gravel or stirred up old gravel, cleaned your aquarium, or added a new carbon filter, and there is a fine white, or slightly brown cloudiness that seems to just hang around. This cloudiness is just dirt that is too fine to be filtered out and does not settle out quickly. Fortunately, particulate cloudiness is the easiest type of cloudy water to fix.


1. Check Your Filter

First, make sure your filter material is properly positioned in your filter, so it is working properly. 

2. Get a Particulate Clarifier

Go to your local pet store and pick up a particulate clarifier, or flocullating agent, such as Nutrafin’s Clear Fast or Seachem’s Clarity.  These are harmless water additives that make the super-fine dirt particles stick (or floc) together, so they will settle, or be filtered out more quickly. 

3. Use Filter Floss

Remove your regular filter foam and replace it with a finer filter mesh or water polishing pad while you are treating. This treatment usually takes a couple of hours to clarify completely.

Part II : Bacterial Bloom (New Tank Syndrome)


Does your water have a white or light brown cloudy haze? If the floculants (particulate clarifiers) do not work, there is a good possibility that the problem is a bacterial bloom.

Bacterial blooms generally occur shortly after setting up a new tank, or when there has been chronic overfeeding, or overstocking of your tank.

Bacterial blooms are an indication that the ecosystem of your aquarium is out of balance, and needs to be restored.  More waste is in your system than your good bacteria can handle, causing a different type of bacteria to thrive. 


1. Check Your Filter

The first step in fixing a bacterial bloom is to make sure your filter is properly sized for your tank and fish stocking levels. 

2. Change Your Water

The second thing to do is a 20-30% water change, making sure you are siphoning the excess fish food and waste out of your gravel. 

3. Reduce Feeding

If while you are vacuuming, you notice a lot of debris coming out of the gravel, you have been overfeeding. Reduce feeding to prevent another bloom.

4. Supplement

Clear your water with biological supplements, such as Nutrafin's Cycle or Seachem’s Stability. Treat for 2 or 3 days at a double or triple dose.

5. Use an Enzyme Mix

If your tank does not clear in a few days, or if you want to speed up the process, Nutrafin’s Bio-Clear directly targets the bacterial blooms with an enzyme mixture.  Enzyme mixes will target the blooms directly, but not fix underlying issues, so check your filter and feeding first. 

Part III : Green Water (Free-Floating Algae)


Does your water look like pea soup? If your water has a greenish tinge that only thickens as the days pass, you have an aggressive form of free floating algae (commonly called green water).  This is probably the most frustrating and ugliest form of cloudy water to get rid of, and is indicative of an imbalance within your tank ecosystem. 

Usually green water starts because of overstocking or overfeeding. The excess waste decomposes, causing high nitrates and phosphates in your system.  These nutrients are algae fertilizer, and can quickly cause an outbreak.


There are a couple of effective solutions for solving this problem. 

Solution 1

1. Use Floculating Agents

Also called particulate clarifiers, floculating agents, like Nutrafin’s Clearfast or Seachem’s Clarity*, can be used the same as when clearing free-floating particles. Often it takes a couple treatments to clear it up.

2. Use Filter Floss

During treatment, you should replace your filter media with filter floss, or a water polishing pad. Filter floss is cheaper and finer than your standard foam, so it filters smaller debris.

3. Add a Nitrate or Phosphate Remover

After your water is completely clear, adding a nitrate and phosphate absorbing filter media, such as Fluval Clearmax, reduces the likelihood of the green water coming back. 

4. Monitor Feeding and Change Water

Monitoring feeding, and doing regular water changes, will also aid in keeping the overall waste levels down so the algae does not return.

Solution 2

1. UV Sterilize

The other solution that is 100% effective and guarantees that neither the bacterial colonies, nor the green water algae will ever return is the addition of a UV sterilizer. UV sterilizers, although more expensive than particulate clarifiers, continuously sterilize the water, killing the algae blooms and free floating-bacteria so you will never have cloudy water again.

Enjoy your crystal clear tank!

*NOTE: These products should never be overdosed.  They are harmless but will not be effective at high levels.

Posted by Amy Dyck

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