GFO Calculator
Enter your aquarium details to calculate the recommended starting amount of GFO needed.
Start slow: GFO removes phosphate quickly and effectively. Begin with the recommended starting dose and monitor phosphate levels closely. If corals show negative reactions after 24 hours, reduce the amount by half and increase gradually over time.
Start Slow: Recommended Dosage
The recommended starting dose is 1 gram of GFO per gallon of total system water volume.
Rinse all new media before use and place it in a media bag, filter sock, canister filter, or fluidized reactor.
Monitor phosphate levels weekly. If phosphate remains above 0.15–0.25 ppm, replace or increase GFO as needed.
If after 24 hours you notice any negative coral reactions, reduce the amount by half.
Why Use GFO?
GFO, or granular ferric oxide, helps remove phosphate from aquarium water. Lower phosphate levels can help reduce nuisance algae and support a cleaner, more stable aquarium.
How This Calculator Works
This calculator multiplies your total system water volume by the recommended starting dosage of 1 gram per gallon. If liters are selected, the calculator automatically converts liters to gallons before calculating the dose.
Supported Products
- Reef Genetics GFO – High quality granular ferric oxide for effective phosphate removal.
- Reef Genetics High Capacity GFO – Higher capacity media for longer-lasting phosphate control.
- RowaPhos – Iron-based phosphate removal media designed to reduce phosphate and help control nuisance algae in reef aquariums.
Pro Tip
Start slow. GFO removes phosphate quickly and effectively. Always test your water and adjust gradually to avoid shocking your aquarium.