Biopellets have been around in the reef aquarium hobby for the past 5 years or so. But a lot of mystery remains when it comes to figuring out what they do, how they do it and the best practices for using them. 

In line with my "Reef it Simple" philosophy, I wanted to break down the confusion around biopellets and answer some questions that you're almost sure to have. So without further ado, here's your introduction to biopellets in the saltwater reef system.

What Are Biopellets?

Biopellets are a biodegradable polymer that is made from bacteria. They act like steroids for the beneficial bacteria in your system. You want a strong colony of this bacteria because it naturally controls the nitrates in a tank. Corals need some small levels of nitrates and phosphates to thrive. But too much of either can lead to problems like coral death or algae bloom.

Biopellets provide an ideal environment for beneficial bacteria to thrive. By pumping water from your system into a biopellet reactor we are creating a controllable, food-filled house where bacteria can live and reproduce.

Biopellet Alternatives

Biopellets provide a source of carbon, but not carbon like the media that we use to remove toxins from the tank. This is carbon as in the building block of life. Because we're feeding the bacteria, you can choose to use some other form of food.

Vodka dosing, carbon additives (such as Red Sea NO3:PO4-X ), sugar and even vinegar are all ways to add carbon. Adding these elements to the system in a broadcast manner can turn the entire tank into an ideal environment for the bacteria. The potential drawback here is that it's less controlled than a reactor.

Should I Use Biopellets?

If there are so many alternatives to biopellets, why would you use them? One reason is that biopellets are so highly effective at lowering nitrates that (when used with heavy protein skimming) the hobbyist can often stop using granulated ferric oxide (GFO). Unlike GFO, biopellets only need to be "topped off", rather than changed out completely, as they are consumed by the bacteria. This lets the hobbyist do less work (and save a bit of money) while enjoying a crystal-clear water column and healthy livestock. A biopellet reactor also confines the majority of the bacteria to a single area. This allows more precise control over the effects that the bacteria will have on the system.

Hobbyists will see the best performance from using biopellets on systems that have a heavy biological load. Those of us who have a lot of fish or tend to feed heavy (or a mixture of both) have probably dealt with problems that this can cause. A bloom of algae or cloudy water, as well as less-than-ideal growth from our corals are common effects from heavy stocking. 

Avoiding Biopellet Problems

Saying that biopellets have problems is a bit misleading. In almost every case that I've seen where people have problems, they come from couple of specific issues:

  • Using the full amount of biopellets from day one, causing a sudden drop in levels, leading to system shock.
  • Not having an effective protein skimmer to remove excess waste from the water.

So if those are the two problems, how do you avoid them?

It's important to remember the biggest rule of saltwater aquariums - stability is key. Hobbyists tend to run into problems when they "chase numbers" and make drastic changes rather than providing a stable environment. Because biopellets are used to control levels, it's easy to get into the bad habit of looking for perfection.

Getting Started With Biopellets

What we're aiming for is a gradual reduction of nitrates. To do this, we need to start with 1/4 or 1/2 the recommended "total dose" of biopellets in the reactor. Set your pump to gently tumble the pellets in the reactor. If they are allowed to be stationary, they can stick to one another. Allow the bacteria a couple of weeks to colonize the pellets, and make sure that you're using an accurate test kit every few days.

After a couple of weeks have passed, and your level drop starts to plateau, add another small amount of pellets. Again, we're looking for a slow decrease. Keep testing your water and looking for another plateau. It has been my experience, and I've heard from other successful biopellet users, that a nitrate level of 0.5 and a phosphate level of 0.03 to 0.05 is fairly ideal. As you approach these numbers, slow the level of pellets that you're adding. Once your tests show these levels consistent, turn off your reactor and mark the level of the pellets so that you know when to refresh them and how much to add.

The other important point here is skimming. As the bacteria consumes the pellets, a "film" of sorts will be produced. This film has a history of causing a cyanobacteria outbreak. (If you care about the technical aspect of why this happens, look for an explanation at the end of this post.) In order to make sure that this doesn't happen to you, you'll need to skim off this waste from the water coming out of the biopellet reactor. Hobbyists have had great results from placing the output of the reactor near the input of the skimmer, but some have even gone so far as to plumb the output line of the reactor to the skimmer. This ensures that absolutely all of the water coming out of the reactor is skimmed before returning to the system.

Finally, don't change your behavior just because you've started using biopellets. One pitfall is that people believe that they need to increase the feeding or population in order to give the system enough "food". But if we're starting from a known point on our nitrate and phosphate levels, we need to keep those levels the same in order to know how much we're reducing. If you want to feed more, or add a school of chromis, do so after you've established your biopellet level and then adjust as necessary.

Though biopellets can seem like a bit of aquarium magic, they're really very simple. We just have to make sure that we're looking at the whole picture instead of focusing on one specific area. By moving slowly, testing religiously and skimming effectively, you too can have a pristine tank with biopellets.

Warning: Technical Mumbo Jumbo Below This Line

Biopellets are often marketed as a nitrate and phosphate reducer, but that's only partially true. There are different organisms that will feed on nitrate versus the ones that feed on phosphates. Biopellets tend toward the reduction of nitrates by boosting the organisms that feed on them. Phosphates will naturally reduce by a certain amount in relationship to the reduction of nitrates. That is somewhere around a 16:1 ratio, whereby a reduction of 16 parts of nitrate will see a reduction of 1 part of phosphate.

With biopellet systems, we're reducing nitrates at a level faster than we can reduce phosphates. Nitrates will often become undetectable when using solid carbon dosing such as what we are accomplishing with biopellets. The remaining phosphates, then, become food for cyanobacteria if it is not skimmed from the water column.

It is imperative that the hobbyist remove phosphates from the system at a level that matches that of the nitrate reduction. This can be accomplished via water changes, but it's certainly not the most effective or simple method. While biopellets can replace the need to run GFO in a system, GFO is a considerably more effective phosphate reducer. However, by over-skimming (or boosting effective skimming via the direction of reactor outflow to skimmer intake), many hobbyists have found it unnecessary to continue the use of GFO in a system with biopellets.