Why Is My Saltwater Aquarium Water Yellow? (And How To Fix It)

One of the most enjoyable things about having an aquarium, (apart from putting in fantastic plants and enjoying the underwater ecosystem) is having clear water so that you can watch your fish! Personally, this is always a highlight for me. Every day when I come home from work and see the aquarium with fish, it makes me happy again!

What I did notice, however, was that it sometimes happened that the water was no longer clear. The water became cloudy and changed color. In my case, the water turned yellow. So I went to investigate and asked myself: “Why is my saltwater aquarium water yellow?

I found the answers and solutions and below you will find everything you need to solve the problem of yellow water in your aquarium!

So, why is my saltwater aquarium water yellow? 

Several common problems cause your saltwater aquarium to turn yellow. There is the possibility that you have an overabundance of organic materials in your tank, there may be expired live plants in the water, you are not treating your driftwood, diatom algae, or the fact that more carbon is needed.

Below is a more detailed explanation of the problems I have mentioned above. Rest assured, the problem you have is normally always solvable!

Why do you have yellow water in your saltwater aquarium?

Organic compounds

As I just described, an abundance of organic compounds is a problem that can explain yellow water. For example, it could be that there is a lot of uneaten food in the aquarium, fish waste that has not been cleaned up, or living plants that are decaying and have had the best of their lives. 


Driftwood can also cause the water in your saltwater. If you use untreated material, the tannins in the wood may cause your water to turn yellow.


Another cause of the yellow water problem may be that your aquarium is too full of fish and/or live plants. This is because an aquarium needs maintenance, and if you have a busy schedule, this can be a problem. This can lead to a chemical imbalance which can cause yellow water in your aquarium.

How do I solve the problem of yellow water in my saltwater aquarium?

That’s a good question and before I answer it, you should read the following. Before you start working on the solutions, you need to know what problems you are facing.

So answer the following questions for yourself. See which problems apply to you.

1) How long has the tank been running?

2) What filtration do you have?

3) What skimmer do you have?

4) What are the water parameters?

5) What lighting do you have and what is the photoperiod?

When you ask yourself these questions, hold them against the standards that are needed to see where your problem is.

1- How long has the tank been run? This will give you more clarity on when the problem started. Look at things that you have changed to see if this is the problem.

2 – What kind of filtration are you using? This is a good way to check that your setup is correct and that your filtration system is working.

3 – The right skimmer can make the difference between a clean water surface and one that is not.

4 – What are the water parameters? Check if there are any changes here that are not “standard”. By this I mean, check if the values are okay and if they fall within “normal”.

5 – What kind of light do you use? This is important because the yellowing of the water can be caused by an algae bloom. This is caused by your light photoperiod.

Now that you have answered these questions for yourself, hopefully, you have a clearer idea of how to solve your problem. For the sake of completeness, here are some solutions to the problem of yellow water in your aquarium to give you an even better idea of where to start!

I would also like to say that yellow water in your saltwater aquarium does not necessarily mean that your fish are dead or in danger. However, it does mean that you don’t want to take that risk. Therefore, please read the following solutions carefully in order to find the best possible solution for your aquarium (and your fish) as quickly as possible!

How do I fix yellow water in my fish tank?

As you have read earlier in this article, an abundance of organic matter is a common problem in yellow water aquaria. In many cases, I see (in my circle of friends and beyond) that organic compounds are abundant (overpopulation also plays a role in this). 

How do you solve this? Suppose you have an overabundance of food and fish poo that has been left behind. Then the solution is simple: Get rid of the food leftovers and the poop. You can often do this easily with an aquarium vacuum. This can simply ensure that your aquarium stays clean. It is also helpful to replace 25% of the water every week.

The same applies to dead or decaying plants in the aquarium. These can also cause the water to turn yellow. Take them out immediately or when changing the water. You will see that it makes a difference.

We have also talked about untreated driftwood which can cause your water to turn yellow. It’s great to use driftwood, but you need to make sure you treat it. The tannins can cause it to turn yellow otherwise. 

How do you solve this quickly and easily? Sounds crazy, but an easy solution is to boil the wood! I know, it sounds crazy, but boil the wood for about an hour.

With small pieces this is fine, but for larger pieces of driftwood, this is not practical. It normally doesn’t fit in a pan. There is a simple solution for this as well.

Take a large container in which you can put the driftwood. Put water in it and let the driftwood soak. Change the water weekly until you don’t see any discoloration of the water anymore. 

The easiest way is of course to buy driftwood that has already been treated!

How do I keep my saltwater clear so that it doesn’t become yellow?

All the above fixes are about when your saltwater tank already has yellow water, but (not) surprisingly, these are also the things you can do to prevent your water from getting yellow at all.

You see, cooking your driftwood before you place it in your tank is a good idea to not only solve the problem of having yellow water, it can also prevent it in the first place.

This is also the case with the other things that I mentioned earlier. Overpopulation? I recommend you don’t do it in the first place, but if you want you should know beforehand that you should keep a rigid maintenance schedule.

What are some other things you can do to make your water less yellow or prevent it from happening?

You can use/do a couple of things.

GAC (granulated active carbon)

Using granulated active carbon is used to purify liquids and gases and therefore can be really handy in keeping your water from turning yellow.


Purigen makes water crystal clear, Removes brown discoloration caused by tannins, Can be regenerated countless times!


Ozone can help you clean your water a bit. In very low concentrations, it can kill viruses, bacteria, and other germs. I have to tell you though that if you want to use Ozone, you can’t use it as the be-all-end-all and sterilize your water completely. This will result in a negative effect on your fish (or vertebrates).

Other things that you can use to keep your tank clean are:

UV Sterilizer, Other oxidizers, and or binders.

Final thoughts

Even though your fish aren’t going to die right away when the water in your tank is yellow, I know that you want to clean it up. Not only for the health of your fish but also for looking at your fish! It can be difficult to watch your fish when the water gets really yellow so that’s all the more reason to keep it clean! I hope the above tips and tricks have thought you enough about why the water in your saltwater tank turns yellow and how you can prevent it!