saltwater aquarium with best biopellet reactor to keep nitrates down

Best Biopellet Reactor Options (Buyer’s Guide)

If you’re a first-time tank owner, you might not know what a biopellet reactor is. If you’re an experienced aquarist, you might want to know more about the best biopellet reactor for your aquarium. This guide will help you learn the in’s and out’s of biopellet reactors so you can make an informed decision for your tank. Our favorite biopellet reactor is the Reef Octopus BR70 Biopellet Reactor.

Biopellet reactors hold biopellets. Biopellets are useful because they help build bacteria colonies of beneficial bacteria. Bacteria can live, thrive, and multiply in your reactor, creating a healthier environment in your tank. Biopellet reactors also help to filter harmful materials out of the water.

When choosing a biopellet reactor, you will want to make a good decision that is appropriate for your tank, given that this will affect the health of your fish and plants. 

Our biopellet reactor guide will help you find the best biopellet reactor for your aquarium.

Best Biopellet Reactor for your Aquarium Options:

No products found.

What is the best biopellet reactor for your aquarium? 

Our favorite biopellet reactor is the Reef Octopus BR70 Biopellet Reactor. Reef Octopus is an established, reputable brand which means you’re getting a great product that is time-tested. It can support medium to large tanks with its flow rate and is still an affordable, good value product. The downside of this option is that it doesn’t come with its own pump so you will need to purchase the pump separately in order to get a working system.

What is a biopellet reactor?

Biopellets are a biodegradable polymer made from bacteria. Biopellets are essentially houses for beneficial bacteria. Beneficial bacteria helps to control the nitrate levels in your tank, meaning your water parameters will be better for aquatic plants and critters.

A reactor also brings all the bacteria in one place, allowing better control over the effects of the bacteria on the system.

Nitrate levels can be controlled by adding carbon sources to the filter. This can be done with carbon additives, vodka, sugar, or vinegar. They feed the beneficial bacteria, but are less efficient and easily controlled than a reactor.

Why do you need a biopellet reactor? 

Biopellets are highly effective at lowering nitrates, especially when used with heavy protein skimming. This combination is so effective that aquarists can often stop using granulated ferric oxide (GFO). The purpose of GFO is to stop algae growth by removing phosphates. Low phosphate levels will help prevent algae outbreaks.

Unlike GFO, biopellets only need to be refilled, rather than changed completely. Over time, biopellets are consumed by the bacteria versus stripped of their nutritional value. This means that biopellets are often less work (only refilled, not complete change) and less expensive over time. 

Biopellet reactors have the most impact on aquariums with a heavy biological load. This can occur from large fish species and/or a heavily stocked tank. Heavy bioload tanks can suffer from algae blooms or cloudy water. In saltwater tanks, they can also suffer from coral growth issues. Biopellet reactors can be considered an essential piece of aquarium equipment for these tanks, much like aquarium wavemakers.

Biopellet Alternatives

Biopellets provide a source of carbon which feeds the bacteria. Bacteria can also eat other sources of food, which means there are viable biopellet alternatives.

Vodka dosing, carbon additives (such as Red Sea NO3:PO4-X ), sugar, and vinegar are possible food substitutes. The drawback to these approaches is that you’re essentially adding bacteria food to the entire tank at once versus a biopellet reactor which is a more controlled environment.  

How do Biopellet Reactors work?

The structure and operation of a biopellet reactor is pretty simple. Water is pumped through the reactor, which stirs the pellets. This is important so they don’t stick together. Clumped pellets are not as effective at housing bacteria. Over time, pellets are consumed and need to be replaced.

When installing your biopellet reactor, don’t start with a full load of pellets. If you do so, you might drop the nitrate too quickly, which can shock your tank. 

Instead, changes should be made gradually by adding ¼ or ½ the maximum quantity of pellets. Leave that for a few weeks and keep testing your water frequently. Once you see the initial decrease in nitrates begin to stabilize, you can gradually add the remaining pellets. We recommend adding another ¼ to ½ of the maximum quantity and waiting a few more weeks, and continuing this process until the maximum quantity is achieved.

How to Choose a Biopellet Reactor

When thinking through your biopellet reactor purchase, there are a number of factors to consider for the best choice for your tank. 


Most manufacturers offer different sizes for different sized tanks. Match the capacity of your aquarium reactor with your tank size. Also pay attention to the flow rate which is marked in Gallons per Hour (GPH). Higher GPH is related to lower nitrate levels.


Make sure you’re purchasing a biopellet reactor with a reliable pump. The pump is an incredibly important element of the process because it needs to consistently pump water into the reactor chamber. If your pump is unreliable, or even worse, prone to failure, you could subject your tank to unnecessary nitrate shocks. 

Company Reputation

Established brands like ReefOctopus have great reputations for quality, reliable products. Since most biopellet reactors are quite in quality and cost, the brand can make the purchase decision difference.


With aquarium equipment, you typically get what you pay for. When evaluating biopellet reactors, you need to be clear if the kit includes the pump or not. This way, you can compare apples to apples when making your decision. Unless you have specific needs when it comes to the reactor’s pump, be sure that the model you buy comes with its own pump. Purchasing them together is often much simpler.

How To Install An Aquarium Biopellet Reactor 

We recommend following the instructions that come with your biopellet reactor. Although it is easy to do, getting stuck on aquarist best practices and online forum recommendations, as opposed to manufacturer-specific instructions is a mistake.

To give you a high-level overview of the process:

First, you’ll want to purchase the best kind of biopellets that will work with your tank size and bioload. Often times, manufacturers will make specific recommendations for their reactors.

Once you have the biopellets, fill up your reactor with the recommended amount of pellets. We do not recommend using 100% of the maximum pellet volume on day one. Start slow with maybe 25% to 50% of the total pellet volume and wait a few weeks. From there, gradually add the remaining pellet volume.

Place the reactor in your tank and turn on the pump! We recommend keeping an eye on the pump and water flow for a few days to make sure everything is working smoothly and consistently.

Best Biopellet Reactor Options for your Aquarium

No products found.

Reef Octopus BR70 Biopellet Reactor

Reef Octopus is an established, reliable brand. This reactor can hold up to 400 ml of pellets which makes it a good option for medium to large tanks. 

This reactor does not include a pump which means you will need to purchase one separately. We recommend finding a pump with a minimum flow rate of 350. This reactor’s recommended flow rate falls between 265 and 400 GPH so you want to make sure you can use this reactor to its fullest capacity. Always check the flow rate of the pump in advance of purchasing.


  • Reactor lids close with fastening screws 
  • Mesh screen contains pellets without blocking water flow
  • Required GPH: 265-400


  • Highly regarded brand
  • Affordable


  • Does not include pump

Accel Aquatics Biopellet and Filter Media Reactor

Although Accel Aquatics might not be as well-known as Reef Octopus, their biopellet reactor is an excellent option with lots of positive reviews. 

This biopellet reactor includes a flow accelerator which is excellent at keeping the pellets in motion to avoid them clumping together. Although all biopellet reactors are designed to do this, this model’s effectiveness at churning pellets is impressive.

This biopellet reactor does not include a pump so plan on the additional purchase when factoring in your budget. This model is attractively priced so it shouldn’t be too much of a ding when purchasing each element separately. There are reports of pumps with flow rates as low as 260 gallons per hour successfully pairing with this reactor. 


  • Uses flow accelerator to consistently keep your biopellets moving
  • Recommended Flow: 150 – 400 GPH


  • Excellent at tumbling biopellets


  • Does not include pump
  • Some users reported issues with leaks

Reef Octopus Beginner OCT-MF300B 2.5 Inch Media Reactor

If you’re looking for a full kit that includes pumps, a customizable set-up, and media, then this Reef Octopus set-up is what you’re looking for. 

This kit is recommended for smaller tanks due to the limitations of the pump’s power and the small size of the reactor. If you want a flow rate above 95 GPH, we recommend purchasing a larger pump separately. Due to this reactor’s small size, you can house it in your small tank’s sump, or you can hang it to the wall of the tank.

This biopellet reactor is extremely flexible in that you can change what type of media you’re using in order to have different effects in your tank.


  • Includes pump
  • Advised for small tanks only
  • Strong brand reputation


  • Small footprint and slim design
  • Great for small tanks


  • Weaker pump makes it difficult to tumble pellets
  • Not effective for large tanks

AquaMaxx Fr-se GFO Carbon and Biopellet Hang-on Filter Media Reactor

This option brings the flexibility. It is a great multi-purpose reactor specially designed for use in smaller marine tanks. This model is media-flexible, which means you can use carbon, GFO, and biopellets.

It uses an up-flow design to keep filter media suspended and evenly dispersed. This helps to ensure maximum contact time between your aquarium water and the media inside the reactor, which helps the media function most efficiently. 

This option does not come with a pump so you will need to purchase one separately. 


  • Recommended for tanks up to 50 gallons (if using biopellets)
  • Easy set-up


  • Easy attachment to sump
  • High-quality construction
  • Flexible with different types of media


  • No pump included

Aquarium Biopellet Reactors FAQs 

How long does it take for BioPellets to work?

Biopellets are not an overnight solution. ​​Aquarists should start slowly with introducing biopellets (to avoid shocking the tank) so expect at least 4-8 weeks for the bacteria population to multiply and start to impact nitrates.  Once the reactor is fully up and running, we recommend letting it stabilize for another 8 weeks in order to get a full understanding of the changes.

The speed at which biopellets work is impacted by a number of variables, including starting nitrate levels, phosphorous levels, current amounts and strains of bacteria in the tank, tank stocking decisions, protein skimmer selection, UV sterilizer selection and more. As you can see, with so many variables at play, each tank is truly a unique ecosystem which must be carefully managed to its individual circumstances.

Are bio pellets worth it?

Biopellets are great for tanks, especially tanks that are heavily stocked and/or use a protein skimmer. In a heavily stocked tank, there’s more waste, nitrates, and algae to keep under control. By supporting colonies of beneficial bacteria, biopellet reactors can help keep the nitrates under control. 

Additionally, biopellet reactors will make your protein skimmers more efficient, so if you’re using a protein skimmer, you should likely be using a biopellet reactor as well.

Do BioPellets remove phosphates?

Yes, biopellets will help to reduce phosphate levels but the impact is not as significant as nitrates. There is a correlation between nitrates and phosphates so you will find that phosphates will naturally dip slightly as nitrates decrease. The corresponding ratio is somewhere around 16:1, which means if 16 parts of nitrate reduce, you could expect a corresponding drop of 1 part of phosphate.

Can you use a biopellet reactor for freshwater?

While biopellets are often used for saltwater fish tanks in conjunction with protein skimmers, they can also be used in freshwater tanks.


Biopellet reactors keep your nitrates in check by supporting beneficial bacteria colonies. Additionally, they help your protein skimmers operate more efficiently. Biopellet reactors come with a lot of different options, so it is important to know the pros and cons of your choice. Additionally, you will need to factor in your aquarium specifics in order to select the best biopellet reactor .

The best biopellet reactor, in our opinion, is the Reef Octopus BR70 Biopellet Reactor. You’re purchasing a product from a reputable brand with a great reputation for quality. It can support medium to large tanks with its flow rate and is still an affordable, good value product.

Do you have a favorite biopellet reactor? How has using a biopellet reactor changed the water parameters of your tank? We’d love to hear about your experiences!

Leave a Comment

Your email address will not be published. Required fields are marked *

This site uses Akismet to reduce spam. Learn how your comment data is processed.