How to Get Rid of Cloudy Fish Tank Water

How to Get Rid of Cloudy Fish Tank Water?

Rid of cloudy fish tank!

How Does? 

If the water in the aquarium is cloudy, the view is severely restricted. Cloudiness can be identified by milky-gray water, by floating particles visible to the naked eye or by light green color. Depending on the color, the water cloudiness has a different cause. Here we describe typical cloudiness that can occur in the aquarium, as well as possible solutions on how to remove them.

Your aquarium water can be cloudy for a number of reasons. First of all, it depends on the color of the water. If it’s green, you probably have an annoying type of algae that is difficult to get rid of. Make sure the aquarium is not in direct sunlight, refresh your aquarium regularly and you can consider purchasing a UV filter.  

If the water is white in color and cloudy, this can have a number of causes. Most likely you have recently filled the tank and are still “starting up”. What you see is a bacterial bloom that will soon disappear (this can be between 1 day and several weeks).  

This bacterial bloom or mini-cycle can also occur if you change a large amount (more than 50%) of the aquarium water or if you have cleaned the filter medium. Try to avoid this.  

Overloading the water and too much food can lead to a light haze. Make sure there are not too many fish in your aquarium, change the water regularly (partly!) And do not feed more than necessary.  

Another cause of cloudy water in the aquarium can be dust from a new ornament or stones that you have recently placed. Do a water change regularly to reduce this.  Bottom substrates such as aqua soil or Akadama can make the aquarium cloudy for the first few weeks but this will disappear on its own.

Visible Suspended Particles

If you can see dirt particles with the naked eye, it can be easily removed with flocculants such as Seachem Clarity or Microbe-Lift Clarifier Plus fresh water. These products bind suspended particles that then settle to the bottom or are absorbed by the filter. If larger deposits occur on the floor due to clumping, these can then be easily vacuumed with a hose. If most of the dirt is captured by the filter, it is recommended to clean the filter media after using the flocculant.

Turbidity caused by suspended particles is often caused by turbulence in the sludge and ground; it may result from eg fish digging the ground or reconstruction activities by the aquarium owner. If turbidity caused by suspended particles is a persistent problem, you should rethink the aquarium filter hardware. Fine-pored materials such as fine filter mats help to mechanically filter dirt particles in the water. However, these should also be cleaned or replaced regularly to prevent clogging of the filter.

Greenish Water, Floating Algae

In this case, algae or bacterial bloom can be assumed. This phenomenon can occur very suddenly and can be triggered, for example, by seasonal fluctuations. For a more detailed description, we recommend the articles “Bacteria bloom” and “Green floating algae”. In both cases, the short-term use of a UVC clarifier can be used to eliminate this.

What is the Cause of Floating Algae or Green Water in Your Tank?

You should look for the cause of floating algae in your aquarium by one of the following factors:

Your aquarium water is too warm. Your tank is too brightly lit.

There is too much waste in the water (especially with goldfish!)

There is a dead fish in the water causing an ammonium peak.

Your aquarium filter is not working properly, so that waste product is insufficiently processed by the bacteria

In addition, poor plant growth can also cause floating algae. Poorly growing plants also produce waste instead of just processing waste as they normally do.

Dead fish aquarium,

Remove dead fish as soon as possible. Source: Pond Aquarium Problem Solver

These factors can therefore also have an influence: You use too few nutrients, which means that plants that grow less well produce more waste (rot).

The CO2 in your aquarium is not good, so they – again – grow poorly and produce waste (decay).

Brown Water, Blackwater Biotope

This is less a question of cloudiness and more discoloration of the water. The water takes on a yellow to brown color cast, which is often triggered by released humic acids. These are initially given off by new roots or new soil. Such a brownish discoloration of the water therefore often occurs in the run-in phase of a newly started aquarium with root wood. Filter media such as Seachem Purigen ensure crystal clear water again in a short time. Alternatively, the discoloration can often be removed by several generous water changes. However, there is no need for action, humic substances are not harmful to aquarium inhabitants in the amounts normally released by the roots.

Easy peasy!

Start with the basics: a good water change! Read my tips on how to refresh your aquarium quickly and efficiently here. If necessary, do a few water changes one after the other if you really have to contend with a heavy case of floating algae. You have to make sure that the water values of the freshwater correspond to your normal water values in order not to stress the fish and plants too much. Check and note the pH, KH & GH and add minerals if necessary during the water change.

Remove the last bits of floating algae with a UV filter. The ultraviolet light from a UV filter attacks the algae spores head-on. I myself do not let the UV filter sit longer than necessary, usually two weeks. Using a UV filter permanently can be harmful because it affects certain parts of the plant nutrition, which causes your nutrition to lose stability.


Combating floating algae in your aquarium is really not insurmountable with this step-by-step plan. On the contrary. Actually, it is especially important to prevent green water by adhering to a number of standard rules:

Avoid waste.

Do regular maintenance.

Keep your plants in top shape.

Is it still going wrong, or are you reading this blog post if you already suffer from floating algae in your aquarium? Then follow my step-by-step plan to get rid of it.


Eric is the founder of Of course, this is his nickname. In terms of the health of the ongoing projects, his identity is hidden for now. He is known around him as a forward-thinking, creative, innovative entrepreneur.

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