Biopellet Reactor: A Guide
A biopellet reactor tumbles biodegradable pellets to fuel bacteria that consume nitrate and phosphate, exported via a protein skimmer.
Overview
A biopellet reactor is a fluidized reactor filled with biodegradable polymer pellets (a polyhydroxyalkanoate-type plastic) used in reef aquariums. The pellets act as a solid carbon source that fuels bacteria, which in turn consume nitrate and phosphate. It is a form of carbon dosing aimed at low-nutrient reef systems.
How it works
Water flows up through the reactor and keeps the pellets in constant tumbling motion, preventing clumping and supplying oxygen to the bacteria growing on them. As the polymer slowly breaks down it releases carbon, and the bacteria use that carbon along with nitrate and phosphate to grow. All three — carbon, nitrate and phosphate — are needed for the bacteria to multiply.
Nutrient export
The nitrate and phosphate are locked into bacterial biomass on and around the pellets. That biomass must then be removed from the water. A protein skimmer downstream of the reactor strips the bacteria from the water column, carrying the bound nutrients out of the system.
Setup and tuning
The bacterial colony generally takes around four to six weeks to establish. The reactor must be tuned so the pellets tumble gently and is normally paired with an adequately sized protein skimmer. Carbon sources such as biopellets are used alongside or as an alternative to liquid dosing of vodka, vinegar or sugar.
Risks
- An undersized skimmer cannot export the bacterial waste the pellets produce
- Rapidly stripping nitrate and phosphate can stress corals
- Sudden bacterial blooms can cloud the water and deplete oxygen
- Requires saltwater reef conditions; not a general freshwater filter
Maintenance
Flow is checked periodically to keep the pellets tumbling, and pellets are topped up as they are consumed. The skimmer is kept running efficiently so it can continuously export the bacteria that the reactor generates.