Why Is My Aquarium Water Cloudy?

Is your aquarium water cloudy and you don’t know why? Aquarium water can become cloudy due to many reasons, but one thing they all have in common, is it usually means there is an underlying issue that could affect your marine life. 

The good news is that there are solutions for dealing with murky aquarium water once you have identified the problem. Let’s dive right in! 

What are the common causes of murky aquarium water?

There are five common reasons that aquarium water becomes murky.

1. New tank syndrome

If your aquarium is still new (only a couple of months old), you are likely experiencing the natural bacterial establishment process. Often called “new tank syndrome”, this is nothing to worry about, as it is a completely normal process when first setting up a saltwater aquarium. 

When an aquarium is first cycled, the water will appear clear, but as soon as the heterotrophic bacteria start multiplying and consuming the organic matter in the water, the water starts to turn white and appear cloudy. 

The next stage is when the algae consume available nutrients in the water. The water will turn a slight green color. Next, comes the secondary bloom as nitrifying bacterial populations establish. And finally, gradual cleaning occurs as the biological filtration system matures.

This cycle usually takes around 4-8 weeks, so if your aquarium is mid-cycling, allow it time to finish and clear the water. If your tank is not new, or the water continues to be murky, there may be another cause. 

2. Suspended particles

Suspended particles in the aquarium water such as aquarium sand substrate, detritus, micro-bubbles, or mineral precipitates. If you have insufficient water flow patterns, heavy fish loads, or poor mechanical filtration, this may be the underlying cause of the murky aquarium water. 

3. Poor water quality 

Maintaining good water quality comes with every aquarium. If the water has suddenly become murky then you should immediately test the water parameters. The most common water parameters to cause murky water in aquariums include: 

• Rapid pH swings which encourage precipitates to form

• Elevated phosphate and nitrate levels that boost algae growth

• Crashes or spikes in alkalinity levels

• Elevated dissolved organic carbon - the water may also appear yellow

Keeping on top of water changes and monitoring water parameters is key, particularly if you have a coral reef tank, as they are more demanding. When water becomes cloudy, it can create a stressful environment to sensitive corals. 

4. Overfeeding 

One of the most common aquarium mistakes with new reef hobbyists is overfeeding. While fish and corals enjoy being fed, overfeeding leads directly to water quality and clarity issues.

• As uneaten food decomposes, it releases organic compounds into the aquarium water

• When fish are fed more food they produce more waste - this dissolved organic matter becomes too much work for filtration systems to process

• If there is more food waste, bacterial populations increase, leading to algae blooms

All the above become the perfect ingredients for murky aquarium water, and even overfeeding premium food specialized for reef tanks can contribute to murky water. So, remember to only feed your fish how much they can consume within a couple of minutes and do not overfeed corals - many corals actually benefit from slightly nutrient-limited conditions, and overfeeding or force feeding corals can contribute to a stressful environment. 

5. Algae blooms 

And finally, algae blooms - one of the most common causes for aquarium water turning murky. Algae are microscopic plants that can rapidly multiply if the conditions allow. This can quickly turn your lovely clear aquarium water into brown, green, or even red (depending on the species) overnight. The most common algae known to turn aquarium water are: 

• Bacterial blooms - these turn the water white

• Phytoplankton blooms- these turn the water green

• Diatom blooms - these turn the water brown

Algae blooms occur due to:

• Imbalanced lighting with poor photoperiod management

• Excess nutrients

• Silicates

• Imbalanced nutrient-to-light ratio

• Skipping the aquarium cycling process

If you ignore an algae bloom it can cause major issues such as stunting coral growth or causing coral tissue recession. 

NOTE: Reef tanks are more susceptible to algae blooms because of their high nutrient environment and aquarium lighting systems. 

How to fix murky aquarium water?

Test the Water Conditions 

Before you try to fix the murky water issue, you should test all major aquarium water parameters.

If the water parameters are not what they should be, this may be why your aquarium has murky water. Testing water parameters also identifies other issues - for example, if the ammonia level is too high, it may indicate that your biological filter has crashed. 

Check your filtration and pump system

Mechanical filtration systems are your go-to when it comes to dealing with particulate matter in a closed system like an aquarium. You should inspect and ask yourself the following: 

1. Is the filter media clogged, bypassing or not running properly?

2. Is the filter sock dirty? If so, replace it - this should be cleaned or replaced every 2-3 days if you have a heavily stocked aquarium. 

3. Is your protein skimmer functioning properly?

4. Is your return pump causing micro-bubbles?

It is surprising how many murky water stories we hear of lead back to simple mechanical problems with aquarium filtration equipment. This is particularly common with newly-installed protein skimmers, as they are more likely to release micro-bubbles. If you need help with your filtration equipment, the Reefco Aquarium team offers fantastic maintenance services. 

Improve the aquarium filtration

If you have tested your filtration system and it is not running as it should, you can try the following points: 

1. Increase the mechanical filtration - you could try adding filter floss or upgrade your filtration system design like adding a cross-flow pump.

2. Add chemical filtration media such as activated carbon and granular ferric oxide (GFO) - this will improve the water clarity by removing phosphates and dissolved organic particles.

3. Install an aquarium refugium - these are fantastic at reducing nutrient levels while also providing beneficial bacteria.

4. If you have a large aquarium system you may want to consider a secondary reaction chamber to provide targeted filtration.

NOTE: If you are using a mechanical filtration system, remember that balance is key - you don’t want it to suck up all the beneficial aquarium plankton that corals thrive on. 

Adopt good feeding practices

As mentioned earlier, overfeeding can significantly contribute to murky aquarium water. To prevent this issue, you should: 

1. Reduce feeding by 20-50% for 14 days

2. Feed small quantities over time

3. Target feed corals if possible

4. Introduce fasting days - most reef fish will be fine without food for 2-3 days however always check the specific requirements for your fish 

When we tell reef hobbyists the above, they are surprised at how something as simple as reducing their feeding routine can improve water clarity and boost coral coloration and polyp extension. 

Improve Water Flow

Optimizing water flow is essential for keeping particles suspended until they are filtered from the water. You can try: 

1. Creating alternative water flow patterns by using a wavemaker or adding more powerheads

2. Eliminating dead spots where waste accumulates

3. Considering gyre-style water flow patterns

By creating strategic flow you will improve clarity and enhance fish and coral health by removing waste that can accumulate on surfaces. 

Consider using UV Sterilization

If algae blooms are becoming the bane of your aquarium life, then installing a UV sterilizer on a separate pump loop may be the answer! UV sterilizers work by disrupting the DNA of algae as they pass through the UV chamber. 

When installing, ensure that there is efficient water flow through the UV chamber and check that the water flow is not too powerful as this can reduce the effectiveness. If you need help installing a UV sterilizer, feel free to reach out to our expert team here at Reefco Aquariums!

Summary

Remember that an established saltwater aquarium takes time to develop over time, and that by combining patience with troubleshooting listed above can quickly resolve most water clarity issues. 

At Reefco Aquariums we are committed to helping aquarium enthusiasts to maintain a thriving marine ecosystem. If you are struggling with persistent murky water, contact the Reefco Aquarium team today - we are always happy to help!