Seachem Matrix 4 L – High-Porosity Bio-Media
Seachem Matrix 4 L – High-Porosity Bio-Media
What is Seachem Matrix?
Matrix™ is Seachem’s flagship biological filter medium—a naturally-sourced, 10 mm porous stone whose internal macropores furnish > 700 m² of habitat per litre for beneficial microbes. That’s equivalent to the external area of 170 litres of plastic bio-balls packed into a single litre of rock!
Unlike plastic media, Matrix offers both external and internal real estate. The outer surface hosts fast-acting Nitrosomonas and Nitrospira that oxidise ammonia → nitrite → nitrate, while the low-oxygen core fosters denitrifying bacteria that convert nitrate to harmless nitrogen gas. The result is complete nitrogen-cycle control in one media basket.
Key Benefits
Triple-action filtration – removes ammonia, nitrite and nitrate simultaneously.
Enormous surface area – > 700 m²/L beats most ceramic rings and far out-classes plastic bio-balls.
Inert & everlasting – will not break down, leach minerals or alter pH; never needs replacing.
Rinse-safe – bacteria live deep inside the rock, so a quick swish in tank water won’t crash your cycle.
Works at any flow – supports denitrification even at higher turnover rates where products like de nitrate™ stall.
Coverage & Sizing
The 4 L industrial-size bag is ideal for sumps, large canisters or pond filters:
| Matrix Volume | Aquarium Volume Treated* | Typical Application |
|---|---|---|
| 4 L | ≈ 3 200 L (≈ 845 US gal) | Marine & FW display tanks, koi ponds, fish-rooms |
*Based on Seachem’s guideline of 250 mL per 200 L of water.
How to Use
Rinse lightly to remove dust.
Place loose in a media tray or inside a coarse filter bag where water flow is highest—after mechanical and chemical stages.
Use 250 mL per 200 L of aquarium volume. For heavy bioloads, double the amount.
Pair with Seachem Stability® for a rapid bio-filter seed, or dose Prime® during first two weeks to detoxify any residual ammonia/nitrite spikes.
Maintenance: Once a month, swish the rocks in discarded tank water to dislodge detritus. Matrix never exhausts—do not replace it.
Ideal Set-ups
| System | Why Matrix Shines |
|---|---|
| High-stock freshwater (cichlids, goldfish) | Handles heavy ammonia output without constant cartridge swaps. |
| Reef sumps & AIO compartments | Fits where ceramic bricks won’t; supports anaerobes for nitrate control even at 10× turnover. |
| Planted tanks | Inert composition won’t raise hardness; deep pores host denitrifiers that curb algae-fuel nitrates. |
| Koi & predator ponds | 4 L bag treats ~3 200 L; use multiple bags in moving-bed or trickle towers for monster bioloads. |
Pro Tips
Layer order: mechanical → chemical → Matrix → pump return for maximum efficiency.
Combine with Purigen® or MatrixCarbon™ to polish water while Matrix handles bio-load.
For nitrate > 20 ppm, add more Matrix or supplement with de nitrate™ in a low-flow chamber.
Safety & Shelf Life
Matrix is mineral-inert, copper-free, plant- and reef-safe. Stored dry, it has an indefinite shelf life—buy in bulk and keep leftovers sealed for future tanks.
Frequently Asked Questions
Do I still need water changes if I use Matrix?
Yes. While Matrix supports denitrification, large, messy systems may still out-pace biological removal. Regular water changes, sensible feeding and good mechanical filtration remain essential.
Can I boil or bleach Matrix to sterilise it?
It’s unnecessary and can damage pore structure. Rinse in de-chlorinated water instead; if you must deep-clean, soak in a diluted chlorine solution for 24 h, then neutralise with Prime® and air-dry thoroughly before reuse.
