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Saltwater Tank Maintenance

Cloudy Water With Nopox

By January 18, 2022No Comments
Nopox by Red Sea

Nopox is a nitrate and phosphate reducer that is popular for nutrient control in marine aquariums. It is labeled as algae management control because it can help to prevent outbreaks by reducing nitrate and phosphate. If you have less of these nutrients, then there is a lower chance of an algae outbreak.

This product by Red Sea, is similar to what people use when they are vodka dosing or vinegar dosing. Basically, it is carbon dosing.

NoPox is short for NO3:PO4-X Nitrate & Phosphate Reducer which is made by Red Sea.

One common issue that arises is getting cloudy water with nopox dosing. This can be fixed by adjusting your protein skimmer, reducing your dosage, or using a UV Sterilizer.

How Does NoPox Cause Cloudy Water

According to Red Sea, the main causes of a bacterial bloom from NoPox dosing is poor skimming and/or poor aeration. You must use a protein skimmer, and if you have one, it needs to run wet. This will help remove waste faster. You also need to have adequate aeration in your tank.

This product is essentially organic carbon dosing. This can cause a massive increase in bacteria. If it produces too much bacteria, it has to go somewhere, so it goes in the water column. This overload of bacteria is what you see that is turning your water cloudy.

There are two types of bacteria in a reef tank; Autotrophic and Heterotrophic. When you add an organic carbon source, like NoPox, it is fuel for Heterotrophic bacteria. They will multiply rapidly. This is what you see that is turning your water cloudy.

NoPox is a very popular product, and it has a great reputation in the reefing community. If you do a lot of research, one common comment is to use less than the recommended dose. It is important to understand how much water is in your tank and sump, and how much product you need to use. If you have a 100 gallon tank, you likely do not have exactly 100 gallons of water in it. You have sand, rocks, and equipment, etc. that is taking up volume in your tank. It is important to understand the proper volume of water, and this is why a lot of people recommend to under dose, and then to slowly ramp it up.

While it is a great and effective product, you need to understand your nutrients before dosing. Make sure that you have an accurate reading of your Nitrate level before you start. Just because your tank is dirty and hair algae is growing does not mean it is due to high nitrates.

Adding this product at a high dose to a low nutrient system can cause some problems.

Bacterial Bloom With NoPox ( NO3:PO4-X )

If your water is cloudy looking, you may be experiencing a bacterial bloom due to carbon dosing. This is an excessive amount of beneficial bacteria in your water column. There can be many reasons why aquarium water turns cloudy and foggy looking. But, if you just started dosing this, you likely have a bloom of bacteria that is in your water.

This is not really a big issue, and it should not pose a problem to your fish or coral. It certainly is unpleasing to look at which is why most people want it taken care of.

Now, if you had a massive overdose, then that is different. You can harm your fish as carbon dosing does reduce oxygen levels. We are discussing a mild bloom that causes your water to cloud up.

How To Clear Up NoPox Cloudy Water (Bacterial Bloom)

You may be able to stop dosing for a few days, and it may dissipate on its own. These are the directions given by Red Sea on a forum where someone was experiencing a bloom. Here are the 6 steps recommended by Red Sea to clear up an bacterial bloom:

  1. 30% Water change per day until the cloudiness disappears
  2. Add extra aeration
  3. Check pH and add buffer if needed
  4. Stop dosing No3Po4-X until cloudiness disappears
  5. Increase water circulation
  6. Set skimmer for wetter skim

1. Water Changes

According to Red Sea, you need to do a daily water change of 30% until the water clears up. This may seem like a large change, and if you have a big tank, it is. If you feel like that is too much, you can certainly drop that down. This is what was recommended by the manufacturer. There are a lot of success stories on reef forums where people did water changes and a lot where they did not do daily changes.

2. Add More Aeration To Your Tank

Your oxygen levels can drop, and you do not want it to get too low. This can obviously have a negative effect on the living creatures in your tank. You can add another powerhead, or you can adjust one that you have to get more surface agitation.

3. Check And Adjust pH

This bloom may change your pH, and you want to make sure that you get your pH to the proper range. If you pH is out of whack, you will need to adjust it and check it daily.

4. Stop Dosing No3Po4-X

The recommendation is to stop dosing the product. I know a lot of people reducing dosing, and that may work as well, but the manufacturers say to stop using it until your water is clear again.

5. Increase Water Circulation

Again, oxygen levels are consumed faster when you have cloudy water due to bacterial bloom. Improving water circulation will only benefit your tank. This will help to clear your water faster.

6. Increase Protein Skimmer

Your water column has excess bacteria in it, and you can increase your skimmer to remove it quicker. If you are not currently producing wet skimmate, you can increase the output of your protein skimmer.

This means that the bubbles will flow into the cup faster. Your cup will collect gunk faster, so you will need to empty it out more. This will help to clear your water. This is one option to try, and it may not work.

It is very important to use a protein skimmer while dosing No3Po4-X. I would not recommend using this product without one. You also need to make sure you produce more skim which is also known as wetter skimmate.

I have experienced cloudy water with nopox before, and the only thing that cleared it up was a UV sterilizer.

Use A UV Sterilizer

A UV Sterilizer can clear cloudy water in 2 to 3 days. A UV light is a great piece of equipment to have for a marine aquarium. For this situation, you do no need an expensive UV Sterilizer. Almost any will do, as long as the size and watt is big enough.

This UV Sterilizer from Amazon is inexpensive and will work on aquariums up to 100 gallons. It is rated at 9 watts for an 80 gallon, but I used it on my 100 gallon and it worked perfectly for clearing my water. In one day I saw a big improvement, and by day 3, my water was crystal clear.

This is the UV Sterilizer that I used, and I had great success clearing up my cloudy water in 3 days.


My name is James, and I am the founder of Saltwatercoraltank. I love everything about the ocean, and my main hobby is saltwater aquariums. Currently, I have 3 tanks that I maintain. I have a 130 gallon mixed as my main, and I prefer softies.

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