Size Your GFO Media Dose
Enter your tank volume and we'll work out how much phosphate/silicate remover to load – based on Seachem's published rates for PhosGuard and PhosBond.
Based on Seachem's published saltwater rates: PhosGuard 85 mL per 200 L, PhosBond 60 mL per 200 L. Running freshwater? Both are dosed lighter – check the product label.
FAQ
How much GFO media do I need?
Enter your tank volume above – it's built on Seachem's published saltwater rates for PhosGuard (85 mL per 200 L) and PhosBond (60 mL per 200 L). Freshwater tanks are dosed lighter; check the label.
PhosGuard or PhosBond – which do I choose?
PhosGuard is a spherical alumina bead that binds phosphate and silicate. PhosBond blends granular ferric oxide (true GFO) with alumina for the same two-nutrient removal, and Seachem markets it as reusable – it can be dried and returned to service until exhausted. Either works; PhosBond is the closer match to "GFO" in the traditional reef-keeping sense.
How do I know when to replace the media?
Test phosphate and silicate about 4 days after installing fresh media. If the reading has stopped falling – typically once it's down around 0.02 mg/L – the media is spent and it's time to refresh it.
Can I run GFO and carbon together?
Yes, though many reef keepers run them in separate reactor chambers or media bags so each gets even, untumbled flow rather than competing for contact time. See our Activated Carbon Calculator.
Shop Phosphate & Silicate Media
Dose rates above are Seachem's published saltwater figures. Running a different GFO brand? Check its own label – dosing strength varies.