PhosNet 125 g — GFO Anti-Phosphate 1.41 mg/g High Capacity | Seachem

Seachem PhosNet 125g is a synthetic granular iron oxide (GFO) filter media offering the highest binding capacity in the Seachem phosphate-removing range at 1.41 mg PO4/g. Its high porosity and large surface area allow for the rapid removal of phosphates and silicates from marine and freshwater aquariums, with stronger binding than most competing products. PhosNet also produces less dust than competing GFOs, making it easier to use.

Main advantages

• Synthetic GFO with the highest capacity Seachem — 1.41 mg PO4/g
• High porosity and large surface area — stronger bond than most competing GFOs
• Less dust than competing GFOs — easier to rinse and use
• Irreversible bond — does not release phosphates or silicates into the water
• Reduces phosphates and silicates to very low levels

Use in reef and marine aquariums

High phosphate levels promote the growth of unwanted algae and compromise coral growth and coloration. PhosNet absorbs phosphates quickly—reaching full capacity in 4 to 5 days in the presence of high phosphates. This rapid replacement rate is a sign of efficiency, not low capacity. Seachem recommends using small amounts continuously rather than large amounts intermittently. The published capacity (1.41 mg PO4/g) is tested at pH 8.4 under real-world aquarium conditions.

Instructions for use

• Rinse before use. Place in a filter bag such as the Seachem The Bag
• Place in a cartridge filter, media chamber, box filter or any high-flow area — do not use in a media reactor (agitation produces dust)
• Dosage: 50 g (½ cup) per 200 L (50 US gallons) of seawater or 400 L (100 US gallons) of freshwater
• Leave in place for 4 days, then test the phosphates. If the concentration has not decreased to 0.02 mg/L, replace the PhosNet
• If the levels remain under control, the product is not depleted — leave it in place and test weekly.
• PhosNet can be removed, dried, and put back into service as long as it is not exhausted.

Comparison of Seachem anti-phosphates

• PhosGuard (aluminum oxide): 0.87 mg PO4/g — the most economical, spherical shape
• PhosBond (GFO + aluminum oxide hybrid): 1.19 mg PO4/g — best capacity-to-price ratio
• PhosNet (pure GFO): 1.41 mg PO4/g — the highest capacity in the Seachem range
• Aquavitro Phosfiltrum (super-capacity GFO): 1.71 mg PO4/g — the highest capacity on the market

Manufacturer's precautions

• Do not use in a media reactor — agitation may produce dust
• Do not overdose — too rapid a drop in phosphates can stress sensitive corals
• PhosNet is not an ion exchange resin and does not release anything into the water.

Available formats

• 50 g
• 125 g
• 250 g
• 500 g
• 2 kg

Why choose PhosNet from ReefSolution?

PhosNet 125g is the ideal choice for aquarists seeking the highest binding capacity per gram in the Seachem range. Place it in the Seachem The Bag for optimal use. For a tighter budget, consider Seachem PhosGuard or Seachem PhosBond. Monitor your phosphate levels with the Hanna Checker Phosphate or the Salifert Phosphate Test Kit.

Frequently Asked Questions

Why choose PhosNet over PhosGuard or PhosBond?

PhosNet (pure GFO, 1.41 mg PO4/g) offers the highest binding capacity per gram in the Seachem range, reducing phosphates and silicates to very low levels. PhosGuard (0.87 mg/g) is the most economical, and PhosBond (1.19 mg/g) offers a compromise between the two.

Can PhosNet be used in a media reactor?

No. Seachem does not recommend it because agitation in a reactor can produce dust, even though PhosNet produces less than competing GFOs. Use in a cartridge filter or media chamber with a filter bag.

How many treatments does the 125g format offer?

At the standard dosage of 50 g per 200 L of seawater, the 125 g format provides 2 to 3 complete treatments. For a 200 L aquarium with controlled phosphates, this represents several weeks of continuous use, with replacement as needed based on testing.