Bioscape Coral Rubble 20-50mm Diameter
Water type
Marine + African Cichlid
Bioscape Coral Rubble 20-50mm Diameter
Chunks of real coral and aragonite that hold your tank's pH and hardness steady. Bioscape Coral Rubble is 20–50mm pieces of coral skeleton and aragonite, sized for building reef structure, sump and refugium media beds, or a buffering base layer under African cichlid rockwork.
Key features
- Coral and aragonite blend — calcium carbonate media that slowly dissolves to release calcium and carbonate into the water column.
- pH and alkalinity buffer — helps hold water parameters stable rather than letting them drift acidic over time, which matters most in marine and African cichlid tanks.
- High surface area — the irregular, chunky pieces give beneficial bacteria plenty of room to colonise, adding biological filtration wherever the rubble sits.
- 20–50mm piece size — large enough to use as structural reef base rock, sump media or a coarse foundation layer, rather than a fine substrate.
Specifications
| Composition | Coral skeleton and aragonite |
|---|---|
| Piece size | 20–50mm diameter |
| Colour | Natural neutral tones |
| Function | pH/alkalinity buffer, biological filtration media, reef and cichlid aquascaping |
Which size do I need?
| Variant | SKU | Price |
|---|---|---|
| 5kg bag | COR03 | $45.95 |
| 10kg bag | COR04 | $79.95 |
Bioscape has not published a coverage or depth figure per kilogram for this rubble, so we can't state how many kilograms you'll need for a given tank footprint here — as a rough real-world guide, rubble this size is normally used as a partial structural layer or sump/refugium media rather than a full substrate bed, so actual quantity depends heavily on your layout.
Coral Rubble vs Coral Sand — which do I need?
Rubble's larger 20–50mm pieces suit structural jobs — reef rockwork bases, sump and refugium media, or a coarse layer under cichlid rock piles. Bioscape Coral Sand's fine 1mm grain is what you want for an even substrate bed that sand-sifting fish and gobies can actually move through. Many reef and cichlid setups use both: sand as the visible substrate, rubble hidden in the sump or refugium as extra buffering media.
Suitable for, and not suitable for
- Suitable for: marine and reef aquariums, African cichlid tanks, sumps and refugiums wanting extra calcium/alkalinity buffering.
- Not suitable for: soft or acidic-water setups — South American cichlids, most planted tanks and blackwater biotopes — where a rising pH and hardness from dissolving carbonate is the opposite of what you want.
Care and maintenance
Rinse before adding to remove dust from bagging and transit. Buffering capacity reduces as the rubble dissolves over years of use; test alkalinity periodically in heavily stocked reef systems rather than assuming it buffers forever.
Warranty and delivery
Each piece is a natural product — size, shape and exact colour vary bag to bag, and photos are representative rather than exact. Any fault on arrival is covered under your consumer guarantee rights under Australian Consumer Law.
Common questions
Will this raise my pH too high?
It buffers pH upward and holds it stable rather than pushing it indefinitely higher — this is exactly what marine and African cichlid tanks are meant to run at, but it's the wrong media for soft or acidic-water species.
How much do I need for my tank?
Bioscape hasn't published a coverage figure, and rubble is typically used as a partial structural or sump layer rather than a full substrate bed, so quantity depends on your specific layout — buy the smaller 5kg bag first if you're unsure and top up.
Can I mix this with regular gravel?
Yes — rubble is commonly mixed with or layered under other substrates for extra buffering, though the buffering effect scales with how much rubble is actually present.
