MarinePure Block 8x8x4"
Water type
Freshwater + Marine
MarinePure Block 8x8x4"
The nitrate-busting brick. The MarinePure Block is a 20 × 20 × 10 cm (8" × 8" × 4") slab of ultra-porous aluminosilicate ceramic biomedia made by CerMedia (USA). Its deep interior is specifically designed to develop the anaerobic zones where denitrifying bacteria live — so it removes ammonia, nitrite and nitrate, something ordinary bio-media can't manage. CerMedia rates it at up to 500 US gallons (around 1,900 L) for general ammonia and nitrite removal, dropping to 150 US gallons (around 570 L) where denitrification is the goal.
Key features
- Removes ammonia, nitrite and nitrate — the deep anaerobic core actively reduces nitrate in passive or low-flow placement, not just ammonia and nitrite like ordinary bio-media.
- Greater than 80% open porosity — water can be poured straight through it; CerMedia describes the internal surface area as roughly 1,000 times that of standard plastic bio-media, though it doesn't publish an absolute square-footage figure.
- Thin Bio-Film Technology — CerMedia's open, interconnected pore structure keeps bacterial films thin, which resists clogging compared with denser media.
- Works as a live rock substitute in minimalist reef scapes, or as sump media in any freshwater or saltwater system.
- Easily shaped with a hand saw or coarse sandpaper if you need to fit an odd-shaped sump (wear a dust mask, rinse before use).
- Inert — won't break down or alter water chemistry over time.
Specifications
| Specification | Detail |
|---|---|
| Material | Aluminosilicate ceramic, fired above 1,000°C |
| Dimensions | 20 × 20 × 10 cm (8" × 8" × 4") |
| Porosity | Greater than 80% open, interconnected porosity |
| Bioload — ammonia and nitrite removal | Up to 500 US gallons (approx. 1,900 L) per block |
| Bioload — denitrification (nitrate reduction) | Up to 150 US gallons (approx. 570 L) per block |
| Water type | Freshwater and marine |
| Manufacturer | CerMedia (USA), sold under the MarinePure brand |
Care and maintenance
- Rinse before use to remove shipping dust — a tap-water rinse followed by a tank-water rinse is enough.
- For denitrification, place it somewhere passive: in the sump, under a gravel bed, or built into the reef structure. Flow through the block should be gentle, not forced.
- Run mechanical filtration upstream so the block isn't doing double duty as a debris trap, and give it a rinse in tank water every few months if flow through it slows down.
Suitable for, and not suitable for
- Suitable for: sumps and filter compartments in freshwater and marine systems wanting ammonia, nitrite and nitrate reduction from one piece of media, and reef scapes using it as a live rock substitute.
- Not suitable for: high-flow placements where you specifically want denitrification — the anaerobic core needs passive, low-flow conditions to work.
Warranty and delivery
Sold with CerMedia's standard warranty against manufacturing defects, in addition to the consumer guarantees you're entitled to under Australian Consumer Law. Ships from Nick's Aquarium Oceanarium Terrarium in Brisbane / North Lakes, QLD.
Common questions
How many blocks do I need?
Size to your tank's total volume against the denitrification rating of 150 US gallons (570 L) per block if nitrate control is your goal, or the higher 500 US gallon (1,900 L) rating if you only need ammonia and nitrite capacity.
Does it work in freshwater?
Yes — CerMedia rates the MarinePure Block for both freshwater and marine systems.
Can I cut it to fit my sump?
Yes. It can be shaped with a hand saw or coarse sandpaper. Wear a dust mask while cutting and rinse the block before it goes in the tank.
Will it work in high flow?
It will still process ammonia and nitrite, but the anaerobic core that drives nitrate reduction needs passive, low-flow conditions — don't expect denitrification from a block sitting in fast-moving return flow.
