So, you just purchased a new biopellet reactor. Congratulations! You may be saying to yourself: “what do I do now”? Hopefully, this article will answer some of your questions.
What are biopellets?
Marine heterotrophic bacteria—bacteria that must “uptake” carbon from sources in the surrounding water column—”feed” on the polymers, and in the process uptake other dissolved nutrients, such as nitrate and phosphate. These bacteria are then sheared from the surfaces of the pellets for subsequent export. As these bacteria live, reproduce, and grow by consuming the media—especially in complex microbial communities called biofilms—they assimilate dissolved nutrients, such as nitrate and phosphate, and other materials, thereby “locking up” these nutrients for subsequent export via protein skimming or mechanical filtration. The added biomass of the bacterial colonies growing on the pellets also results, to a certain extent, in nitrate and phosphate being metabolized to less problematic forms, regardless of export.
The main materials contained in this media are organic polymers. Most biopellets available to aquarists are comprised of either P3HB (poly(3-hydroxybutyrate)) or P3HBV (poly(3-hydroxybutyrate-co-3-hydroxyvalerate). These polymers were developed as potential materials to be used in the manufacture of biodegradable packaging materials. They are made by “coaxing” certain species of bacteria to produce them as a food source. In essence, biopellets are bacterial food, made by bacteria. Many products contain other materials in addition to polymers, such as fillers or ceramic nucleants.
Setting up the reactor: flow, volume, and location
As to the amount of media, I suggest, as a general rule, not to fill the reactor more than half-way full. This allows for a more even and controllable flow through the reactor. Stated differently, reduced volume increases the effectiveness of flow rate adjustments.
As to the flow rate, the conventional wisdom has been to increase the flow until the top layer “gently tumbles.” I still think this is a good starting point, but I strongly suggest testing NO3 and PO4 levels with reliable test kits or meters at least twice a week, starting about 21 days after first setting up the reactor. If you are seeing a consistent decrease in nutrient levels, your flow rate is probably at a good point. If dissolved nutrient levels cease dropping, try increasing or decreasing flow rates until you see NO3 and PO4 levels start to drop.
Be aware that PO4 levels may not drop to very low levels with this methodology. Along with many other aquarists, I have had to use phosphate adsorption media such as granular ferric oxide to get PO4 levels to .05 ppm or below when running biopellets. I have also noticed more effective nutrient reduction, including of PO4 levels, when I also dosed a liquid labile organic carbon source, such as a mixture of ethanol (vodka) and acetic acid (vinegar) in addition to using the biopellets.
Additionally, I suggest turning up the flow in the reactor for 30 seconds every day or two, and then returning the flow rate to the original level. This increases the sheer force on the biofilms growing on the pellets, dislodging existing colonies, and may enhance nutrient reduction by making more space available on the media for bacterial colonization and promoting more rapid growth of suitable bacterial populations.
About Murray W. Camp
Murray is a reef aquarist with over seventeen years’ experience in keeping marine aquaria, from 5 to 800 gallons. He is also a nationally recognized speaker who presents at reef conferences and events around the country, and is an author whose articles have appeared in CORAL Magazine and other publications.
In addition to moderating the TEAM Marine Depot forum on Probiotics and Labile Organic Carbon Dosing, he serves on the Board of Directors of MASNA—the Marine Aquarium Societies of North America—where he is actively involved in conservation and legislative issues.