Cloudy, whitish aquarium water: what should I do?

Whitish and cloudy water in an aquarium. What to do?

Every fish hobbyist has experienced the dreadful episode of encountering cloudy water.

There is a good chance you are dealing with a bacterial bloom or unwashed substrate. Your water may also contain a few visible particles if it becomes totally or partially opaque.

Identify the type of cloudiness at a glance

The color and time of appearance of the cloudiness say a lot about its cause. Before adding any product, observe your water.

If your water is turning green, the problem comes from microscopic algae and not bacteria: consult our article instead I have algae in my aquarium, what should I do?

Basic checks

Whitish and cloudy water in an aquarium can have several causes. Here are some steps you can follow to resolve this problem:

1. Check water parameters: ensure that your aquarium water has the proper pH, hardness, and temperature for the fish living in it. An inadequate pH or temperature can be the cause of water turbidity.

2. Clean the filters: make sure your aquarium filters are clean and in good working order. If the filters are clogged or defective, it can lead to cloudy water.

3. Change part of the water: if the filters are clean and the water parameters are good, it is possible that the water is simply dirty and needs changing. Change part of the aquarium water to see if it improves the appearance of the water.

4. Check plants and decorations: plants and decorations can sometimes be the cause of cloudy water. Ensure there are no rotting leaves or decomposing decorations in the aquarium that could contribute to water turbidity.

5. Consult an aquarium expert or specialist if you have followed all these steps and the water in your aquarium remains whitish and cloudy, it is possible that the fish are sick. In this case, it is recommended to consult a veterinarian for further advice.

The case of a new aquarium

If it is a new aquarium, cloudy water is often initially caused by limescale that needs to "precipitate". This is often the case in freshwater if your tap water is heavily mineralized. This veil generally dissipates on its own. A water conditioner like Aquatan remains useful at each refill to neutralize chlorine and bind heavy metals in tap water, but it does not act on limescale.

If it is a new aquarium, the water is often milky. There are many bacteria that will start to develop to create the nitrogen cycle and "cycle" your aquarium. The problem should resolve in a few days. If you wish to speed up the process, you can use solutions like bactocool.

To secure this phase, adding nitrifying bacteria helps the filter colonize faster. Always follow the dosage indicated on the product sheet: for example, for Aquipond Aquarium Nitriboost, 10 ml for 50 liters every two days for two weeks at startup.

Mistakes that prolong the cloudiness

The step-by-step protocol

1. Test the water : ammonium, nitrites, and pH. If nitrites are present, you must act quickly (see our nitrite emergency protocol).
2. Reduce feeding for a few days, giving only what is eaten in 2 to 3 minutes (see how much food to give).
3. Change part of the water, about 20 to 30%, with conditioned water at the same temperature (see how to change aquarium water).
4. Check the filter : correct flow rate, media rinsed with aquarium water if they are clogged.
5. Seed if necessary with bacteria, at the dosage on the label, then let it act without adding other products.
6. Wait and observe : bacterial cloudiness usually resolves in a few days. Retest the water before concluding.

For more precise measurements, discover our aquarium water analysis tests.

Preventing the return of cloudy water

• Rinse the substrate and decor thoroughly before installing them (see how to clean sand in an aquarium).
• Condition all new tap water before pouring it in.
• Feed sparingly, and remove leftovers and damaged leaves.
• Maintain the filter without ever cleaning everything at once (see understanding aquarium filtration).
• Perform regular partial water changes rather than large, rare ones.

To go further, read our guide how to get crystal-clear water in an aquarium.

Frequently Asked Questions