Can Bio Balls Be Used In A Saltwater Aquarium? Maybe!

Bio Balls are a staple for filtration in the freshwater hobby but when many of those hobbyists move to saltwater this question gets asked over and over again. This article is going to fill in the blanks to why Bio Balls are best left out of a saltwater aquarium.

Bio Balls can be used in saltwater aquariums but if left uncleaned they easily trap detritus which can lead to high nitrates & phosphates. They provide a large surface area for nitrifying bacteria to colonize however newer technology is available to work more efficiently & require less maintenance.

Read on to find out why Bio Balls are not good for filtration in a saltwater aquarium and see what alternatives there are to provide a much better way to achieve biological filtration within your system.

What Are Aquarium Bio Balls?

Aquarium Bio Balls
Bio Balls

In their most basic form, Bio Balls are an engineered complex shape of plastic with the aim to provide the maximum amount of surface area for a given volume of space.

The surface is used to colonize Aerobic Nitrifying Bacteria that convert Ammonia to Nitrites, and Nitrites to Nitrates.

What Do Aquarium Bio Balls Do?

As the water trickles through the Bio Balls in a trickle filter, it allows Aerobic Nitrifying bacteria to grow. Aerobic Bacteria is a type of bacteria that thrive in an oxygen-rich environment. This type of bacteria forms the basis of the first 2 parts of the Nitrogen Cycle:

Converting Ammonia to Nitrites
Converting Nitrites to Nitrates

>>To find out more on the Nitrogen Cycle you can read my article HERE on the aquarium Cycle<<

The Nitrogen Cycle is a constantly running process in your aquarium and it is how mother nature turns waste into less toxic compounds that your fish, invertebrates, and corals can tolerate in small amounts.

Trickle Filter
Typical Trickle Filter

The key in every aquarium is to ensure there are enough Nitrifying Bacteria to cope with the amount of waste within the aquarium. Bio Balls were created to help grow the number of bacteria within a given volume.

Can Bio Balls Be Used In Saltwater Aquariums?

30 years ago they were a great product, or so many people thought. With the advances in technology and experience, we have found ways to look deeper into the microscopic levels of aquarium filtration to engineer better and more ways to help keep our livestock healthy.

So why should Bio Balls not be used in a saltwater aquarium? As you are in your research phase of a saltwater aquarium I’m sure you are seeing on the forums many people calling them ‘Nitrate Factories’.

Many hobbyists found some success with Bio Balls because they regularly cleaned them to ensure detritus was not becoming trapped in the balls, then breaking down and releasing Ammonia, Phosphates, and Nitrates.

The true reason why Bio Balls are not good for saltwater aquariums is more scientific:-

Earlier I mentioned that Bio Balls provide a great environment for Aerobic Nitrifying Bacteria. However, because the water generally trickles through Bio Balls they do not provide a good habitat for bacteria that grow in Oxygen-Depleted environments.

This type of bacteria is known as Anaerobic Nitrifying Bacteria.

Aerobic & Anaerobic Bacteria

Aerobic Bacteria:
Convert Ammonia to Nitrites
Convert Nitrites to Nitrates

Anaerobic Bacteria:
Convert Nitrates to Nitrogen Gas

Without Anaerobic Bacteria the only way to prevent Nitrates from building in your saltwater aquarium is by regular cleaning and maintenance and frequent water changes.

With Anaerobic Bacteria you have another janitor on your filtration team to help remove the Nitrates by converting it to Nitrogen gas which then bubbles out to the water’s surface.

Anaerobic bacteria grow in areas of low flow and low oxygen – Two areas already mentioned that you will not get when using Bio Balls. So how do you get areas in your filtration with low flow and oxygen? Read On to find out…

Are There Alternatives To Aquarium Bio Balls?

The two most popular areas for colonizing both Aerobic and Anaerobic Bacteria are Live/Dry Rock and Live Sand. Myself included, many new aquarists to the saltwater hobby have no idea why there is such a big hype when it comes to using Live or Dry Rock and Live Sand.

My Reef – Day One. Dry Rock & Live Sand

We all just used rocks and gravel in our freshwater tanks so why can we use that in a saltwater aquarium? The main reason is that freshwater fish can tolerate incredibly high levels of Nitrate compared to their saltwater counterparts.

The Live/Dry Rock and Live sand proved the massive surface area needed to grow sufficient amounts of bacteria that are required to process the waste to levels in which sensitive marine life can tolerate.

The third alternative is a fairly new product called MarinePure. It is a manufactured material filled with cavities and tunnels to provide immense surface area for both Aerobic and Anaerobic Bacteria. Many aquarists place blocks or spheres of this material in their sump to increase the growing areas to ensure their system has the most bacteria available to process waste.

MarinePure Aquarium Media

To find out more about MarinePure you can see it HERE at

Can Trickle Filters Be Used On A Saltwater Aquarium?

If you have been using an old-style trickle filter with Bio Balls and you find its time for an upgrade or you have been battling high Nitrates you may have just figured out why.

The main thing with anything saltwater is to slowly make ANY change. If I was in this situation here is what I would do to make a filtration switch.

Chances are that if you are running a trickle filter you have the room under your stand to replace it with a sump!

  1. Remove Trickle Filter and place the sump in the same location
  2. Remove the Bio Balls from the trickle tower and give them a rinse in a bucket of aquarium water – Discard that water
  3. Place the Bio Balls into a mesh bag in the sump to keep them all together.
  4. Add in one brick of MarinePure
  5. Each Week remove Bio Ball bag and rinse in a bucket of tank water
  6. Remove 25% of the Bio Balls and discard
  7. Repeat Steps 5&6 until there is enough room to add another brick of MarinePure
  8. Finally, remove all the BioBalls and enjoy your new sump setup

How Do You Clean Aquarium Filter Media?

No matter what filter media you run you need to be careful about how you clean it. Regular cleaning is the only way to keep Detritus from collecting in it and begin to break down.

Many people making the jump from freshwater just wash their filter under the tap. Do this in a saltwater aquarium and get ready for a Tank Crash! The beneficial bacteria is your friend and you need to do everything you can to keep your colonies healthy.

Do Not Ever Wash Your Filter Media Under A Tap!
It Will Kill Your Nitrifying Bacteria

As mentioned above, the best way to clean any filter media is during a water change. Before dumping the water removed from the aquarium down the drain, just grab a couple of buckets full and then give your filter media and gentle shake in those buckets. You will be surprised how much brown junk comes out of the cleanest looking media!

Another great tip just before your water change is to Mag-Clean your glass and give ALL your rocks, MediaPure Blocks and sump a good blast with a turkey baster. Get all that dirt into the water column, then do your water change!

After implementing this regimen you will find you will have fewer detritus each week and therefore less breaking down and releasing Nitrates and Phosphates.

Further Reading

You may find these articles helpful in your research:


Hi, I'm Richard and I have been an avid aquarist for over 30 years with a passion for Saltwater Aquariums. I love to pass on my knowledge to help others get the same amount a pleasure out of this hobby as I do. View my About Me page to find out more about me & my mixed reef aquarium.

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