Why Does Betta Fish Water Get Cloudy?

First-time betta keepers commonly experience issues with cloudy water, which can be caused by things like bacteria, pollutants, or too much light or fish food.

It’s a frustrating problem and one that can seemingly come from nowhere. You might go to sleep with clear water and wake up to cloudy water, and it might turn clear again just as quickly.

You’ll be relieved to know that even experienced fish keepers have to deal with cloudy water from time to time, and fortunately, cloudy water is not necessarily an emergency. You can usually resolve the issue by following some simple steps.

By Martin FischerParostoteles[CC BY-SA 3.0]

Why Does Betta Fish Water Get Cloudy?

Cloudy water may turn a few different colors, depending on what’s affecting your tank.

White or gray water is the most commonly seen cloudy water in betta tanks. It’s the trickiest to diagnose because there are a few different causes.

Dirty Gravel

If your tank becomes cloudy immediately after filling or changing the water, the most likely culprit is dirty gravel. Even gravel bought brand new from the store could carry dust or other particulates.

The same is true for fake plants, rocks, and other aquarium items.

Rinse everything under fresh, running water for at least 30 seconds before introducing it into your tank and whenever you change the water.


Putting too much food in the tank can lead to particle buildup, which makes the water look dirty or cloudy.

Don’t feed your fish too much at once. It’s better to feed them a little bit throughout the day than to dump a lot of food in the tank at one time.

Also, give your fish a fasting day once a week where you don’t feed them at all. The fasting day allows them to completely digest and process their food and prevents overfeeding.

Too Many Fish

This is another common cause of gray cloudy water. A closed environment like a fish tank can’t sustain as many fish as a natural environment like a pond.

This is because the system relies on you to maintain it. Too many fish in the tank overload the filtration systems, leading to the buildup of waste and bacterial bloom.

A good rule of thumb is to allow at least five gallons of water for every fish in your tank. If the water is cloudy because you have too many fish in there, partially change the water, clean the tank, and rehome some of your fish.


If you’ve washed your gravel, aren’t overfeeding, and don’t have too many fish in your tank, cloudy water could be due to dissolved particles in your tap water.

Test the pH of your water. You’ll likely find that it’s alkaline, due to dissolved silicates, heavy metals, and phosphates.

Treat your tap water with a conditioner or pH buffer before putting it in your tanks.

Bacterial Bloom

Bacterial bloom happens in just about every new tank setup. It happens as the tank’s biological filter establishes itself.

A biological filter is a natural “filter” made of bacteria. The bacteria eat leftover food and fish waste and help to keep the tank clean.

Initially, there aren’t enough bacteria in the tank to handle the waste. So at some point, usually within the first week or two, the bacteria will “blossom,” or bloom.

The excess bacteria will turn the water cloudy.

A bacterial bloom is a natural part of the ecosystem of your tank. It’s nothing to panic about and usually resolves within a few weeks.

In the meantime, keep cleaning the tank regularly to remove excess waste and food.

A bacterial bloom can also happen after a big water change because you remove many existing bacteria when you remove the old water.

Yellow Water From Tannins

It’s unlikely that you’ll see yellow water in your tank, but it does happen occasionally. Usually, the cause is tannins.

When wood soaks in water, the tannins leach out, discoloring the water and lowering the pH. Tannins aren’t necessarily harmful, and many species of tropical fish thrive in water that contains tannins.

If you plan to put wood in your tank, soak it in fresh water for a few days first. Soaking will allow the tannins to leach out before you put the wood in your tank.

If you buy wood from a pet store, it should come pre-soaked.

Too Much Light

There is only one cause for green cloudy water: algae bloom. If your tank is near a window or you leave the aquarium light on too much, this can cause algae to bloom in excess.

Try not to place your tank by a window. It makes controlling the temperature and light very difficult.

Put your tank somewhere without a lot of natural light and use an aquarium light to light it.

Don’t leave it on all the time; 10-12 hours a day is sufficient to light the tank. Turn the light off overnight to prevent algae blooms.

Too Much Phosphate

Excess phosphate comes from fish and food waste. It can also be found in large quantities in some tap water.

If you notice gray cloudy water followed by green cloudy water, you may be overfeeding or have too many fish in the tank.

If you’ve already controlled for overfeeding and overcrowding, test your phosphate level. If you find that the level is too high in your tap water, consider using bottled water for the tank instead.

Is Cloudy Water Harmful to My Fish?

Cloudy water is not immediately harmful to fish but left untreated it can lead to problems. In particular, gray and white cloudy water from dirty gravel or pollutants can be harmful.

If the density of pollutants or particles is very high, it can damage fish gills or even suffocate them.

If you notice the water in your tank is cloudy but your fish seem fine, wait a few days. The problem may resolve itself.

If it doesn’t, try cleaning the gravel or doing a partial water change, or take a sample of the water to your local aquarium supply store.

Final Word

Cloudy water is scary for a first-time fish owner, but it’s usually not a big deal. Often the problem will resolve itself, and if it doesn’t, there are simple steps you can take to fix the underlying issues.