13 Ways To Keep Your Saltwater Tank Crystal Clear

I really like having a dirty saltwater tank. Said no one.

Keeping the water in your tank crystal clear can be a bit of a challenge at times.

Everyone who has kept a saltwater aquarium has struggled with this at one point or another. Maintaining a clean tank where the water is clear is a goal we all strive to achieve. 

By following a few tips, you can easily have crystal clear water in your saltwater tank that will have it looking like a showpiece in no time. 

I have used each of these methods at some point and they are all effective. You won’t want to use them all together at the same time, but choose the ones that will work best for you and your tank. 

Tip #1. Use RODI water

Every saltwater tank owner should be using RODI water. Tap water should not be an option and there are many negative effects of using it. Reverse osmosis deionized water will provide you with water that measures 0 TDS (total dissolved solids) which is what all saltwater tanks should have.

Tap water will normally have nutrients of phosphates, nitrates, and silicates which are all harmful to saltwater tanks. Other chemicals found in tap water are calcium, magnesium, chlorine, and chloramine. Using RODI water will help keep your tank water clear while keeping the nutrients and chemicals out.

I recommend using a quality RODI filter system to make pure water for your saltwater tank. The Aqua FX RODI unit is affordable and works great. It is available on Amazon here. You can choose to purchase water from your local saltwater store if they provide it and you know it is tested. But over time this can get expensive and it will be cheaper for you to use your own filter system.

You can control the filter changes when necessary, make water when needed, and it’s more convenient. 

Tip #2. Use an aquarium UV sterilizer

Using an aquarium UV sterilizer is a great way to achieve crystal clear water. There are different types available to use but basically a UV sterilizer is a waterproof casing that has a UV bulb inside This bulb will kill any undesirable free-floating organisms that pass through the unit.

Things like parasites, algae spores, and bacteria that can be harmful to your tank and cause bacterial blooms and cloudy water. You don’t need to use a UV sterilizer constantly.

They can be used temporarily to clear cloudy water in the event of an algae bloom. They are very beneficial in helping keep your tank water crystal clear and healthy.

Choosing the right size UV sterilizer for your tank is important as you want the unit to be as effective as possible.
This will lead to excellent water quality and crystal clear water.

Tip #3. Perform a water change

If you are dealing with cloudy water, perhaps it’s time for a water change. Regularly scheduled water changes will really help in keeping your water clear. Depending on the size of your tank, you might choose to perform a 10% or 20% water change. If you are dealing with a water quality issue, you might want to do more.

Even though a water change will help clear up the water in your tank, it’s important to perform water changes consistently as this will help with keeping your water clear on a long term basis and not just to fix a water issue you may have.

Water changes are a generally good thing for your tank which will help keep your tank healthy. 

Tip #4. Have good filtration 

Every aquarium needs a filtration system of some kind. It’s common for saltwater tanks to use various methods of filtration such as a sump or refugium. You can also use hang on the back filters, and canister filters. Each method of filtration will have its pros and cons.

The best filtration for a saltwater tank comes from the live rocks. Many hobbyists use live rocks as the main source of biological filtration for their tanks. Chemical and mechanical filtration is important as is biological. Live rocks will house beneficial bacteria needed to keep your tank established and healthy.

Excellent filtration is a great way to keep your saltwater tank clean. 

Tip #5. Remove uneaten food

This is something that not many people do but you really should.

Overfeeding your fish and corals is a leading cause of poor water quality in the aquarium hobby. Only feed your fish as much as they can eat in a short amount of time. The more they eat the more waste is produced causing elevated levels of nitrate and phosphates.

Food that doesn’t get eaten will sit in your sand bed and rocks causing poor water quality. Removing this uneaten food will not only help in improving your water quality, but your water will be clearer. 

Tip #6. Clean algae off the glass

Removing algae that form on your glass is a great way to keep your water clear. Many forms of algae can grow on your glass including diatoms which just make your tank look dirty.

If you remove these algae and prevent it from forming, your tank will stay very clean looking. Do this as part of your regular maintenance routine. It only takes a short time to do and is a big part of keeping a spotless tank. I use the Flipper algae cleaning magnet. They are awesome. You can get one on Amazon here.

Click the image to read a review of the Flipper

Tip #7. Use activated carbon

Activated carbon media is used for a few reasons but many people use it for water polishing and keeping your water clear. This can be used inside of a media reactor or media bag which is then placed in your filter or sump. It helps remove contaminants, toxins, odors, and should be changed often.

Carbon is a simple and affordable way to quickly have crystal clear water in your tank.

Tip #8. Use filter socks and filter floss

If you have a sump system on your tank, you most likely are using filter socks. Not everyone likes using filter socks due to the amount of frequent cleaning and changing out that they need. Filter socks are very beneficial in removing small and large particles from your aquarium water and does a great job in keeping your water clear.

Filter floss and padding work the same way. You can easily add this to any filter which will trap debris from the water creating clear water.  

Learn how to clean your filter socks here.

Tip #9. Use a water clarifier

There are certain products that you can buy which you add to the tank water to help it clear up. It will help clear and maintain clear water by clumping particulates together so they can be filtered out. Most products are safe to use and do not contain harmful chemicals. Marine Depot sells some great options. 

Tip #10. Use a protein skimmer

A protein skimmer is a great method of nutrient export in saltwater tanks. There are other methods as well but using a skimmer is very effective. Hang on tank or in sump style protein skimmers are a very important piece of equipment and although they are not necessary, they should be used if possible.

Yes, protein skimmers are effective in removing waste from your water but they are also great for helping to keep your water crystal clear.

Tip #11. Don’t overstock your tank

This is a very common mistake that we all have made from time to time. Who doesn’t want a tank full of awesome fish? The problem with having too many fish in the same tank is those fish produce a lot of waste and will lead to poor water quality and health concerns.

A heavily stocked tank will require more attention and maintenance from you and if it gets out of hand, your water quality will really suffer. You will have a difficult time keeping your tank clear if it is overstocked. So keep your stocking levels low and you will have much clearer water. 

Tip #12. Keep your sand bed clean

This might sound like common sense but not everyone pays attention to keeping a clean sand bed. Many times we perform water changes and just let the detritus sit there unremoved. This will definitely cause poor water quality leading to dirty water and an overall dirty looking tank.

So remove all uneaten food and waste from your sand bed to have a clean looking tank. 

Tip #13. Use a refugium with macroalgae

Refugiums with macroalgae like chaetomorpha is a very popular method of nutrient removal. Most sump tanks will have a refugium section and there are hang on tank options if you are not using a sump. They are effective in keeping the nitrate and phosphate levels low.

Using a refugium light to grow the macroalgae, these nutrients can be removed by harvesting the algae out of the system as it grows.

This will lead to excellent water quality and crystal clear water. 

 Why is my aquarium cloudy?

If you have a new saltwater tank, it will take time for your water to clear. It will naturally go through a cycle which over a 4-8 week period, your tank will clear up. If your tank is already established, the reason your water might be cloudy is due to particulates in the water not being filtered properly. It’s also possible to experience an algae bloom that causes cloudy aquarium water. This is caused by excess nutrients in your tank.


Keeping your saltwater tank crystal clear is not a difficult task. Following a few of these important tips will be very helpful. Proper maintenance, planning and patience are all important things with saltwater tanks. Choose from the methods above to get your tank looking as clean as possible.