MarinePure Fresh GEMS 50g
Pack size
50 g
Water type
Freshwater
MarinePure Fresh GEMS 50g
Ultra-porous ceramic biomedia sized for nano and small canister filters. MarinePure Fresh GEMS are small ceramic pellets made by CerMedia (USA) from the same aluminosilicate ceramic as the full-size MarinePure Spheres and Plates, fired above 1,000°C to create a rigid, open-pore structure. Each pellet is about 19 mm (¾") across, so the 50 g box suits hang-on-back and small canister filters on freshwater community, planted and tropical tanks, where a full block or sphere box would be overkill.
Key features
- Ultra-porous ceramic — an open-pore structure gives bacteria far more surface to colonise than a plastic bio-ball or ring of the same size.
- Handles the nitrogen cycle — the porosity is designed to support ammonia- and nitrite-processing bacteria, with nitrate reduction in the low-oxygen pore centres over time.
- Resists clogging — the ceramic structure holds its shape, so flow through the media stays consistent between cleans, unlike foam or floss.
- Reusable — rinse in tank water at a water change rather than replacing on a schedule.
- Fills odd-shaped spaces — loose pellets pack into media baskets and hang-on-back trays that a block or plate can't reach.
Specifications
| Brand | MarinePure (CerMedia, USA) |
|---|---|
| Pack size | 50 g |
| Pellet size | Approx. 19 mm (¾") diameter |
| Material | Inert aluminosilicate ceramic, fired above 1,000°C |
| Open porosity | 80–90% |
| Surface area density | Approx. 1.3–1.7 m² per gram (CerMedia's published material rate) |
| Total surface area, this box | Approx. 65–85 m² (700–915 sq ft), calculated from the rate above |
| Water type | Freshwater |
| Filter compatibility | Canister, hang-on-back and internal filters with a media basket |
Which GEMS box do I need?
GEMS come in two sizes, and the right one depends on the filter as much as the tank.
| Pack | Surface area | CerMedia bioload guidance | Best suited to |
|---|---|---|---|
| Fresh GEMS 50 g | Approx. 65–85 m² (700–915 sq ft) | Tanks up to 40 US gal (150 L) — CerMedia's own filter-sizing guidance for this pack | Freshwater community, planted and tropical tanks in small canisters or hang-on-back filters |
| GEMS 90 g | Over 135 m² (1,450 sq ft) | Up to 70 US gallons (265 L) | Freshwater and marine nano and small tanks |
CerMedia rates the two GEMS packs separately rather than one being scaled from the other: tanks up to 40 US gallons (150 L) for the Fresh GEMS 50 g pack, and up to 70 US gallons (265 L) for the 90 g box. Both figures come from CerMedia's own site.
Suitable for, and not suitable for
- Suitable for: freshwater community, planted and tropical aquariums running a canister, hang-on-back or internal filter with a media basket small enough for loose pellets.
- Not suitable for: the sole biological media on anything beyond a small tank — for larger systems, MarinePure Spheres, PODs or a Plate carry far more surface area per dollar. Not a mechanical or chemical media either — it won't polish water or remove odours on its own.
Care and maintenance
Rinse GEMS in tank water or dechlorinated water at a water change — never under tap water straight from the mains, since chlorine and chloramine will knock back the bacterial colony. There's no fixed replacement interval; the ceramic doesn't wear out, so GEMS keep working until the filter basket is due for a clean.
Goes well with
- MarinePure Mesh Bag (Small) — keeps loose GEMS contained and easy to lift out for a rinse.
- A water conditioner — dechlorinate top-up water before it reaches the filter, so new water doesn't strip the bacterial film.
- An ammonia and nitrite test kit — confirm the media is cycled before stocking up.
Warranty and delivery
MarinePure Fresh GEMS has no stated wear-out life from CerMedia — it's ceramic, not a consumable cartridge — and any manufacturing fault is covered by your rights under Australian Consumer Law in addition to any retailer or manufacturer terms. Standard parcel freight applies.
Common questions
Can I mix GEMS with other filter media in the same basket?
Yes. GEMS are commonly run alongside mechanical floss or sponge for particles, and chemical media such as carbon for odour and colour, as long as the basket still lets water pass through the GEMS rather than around them.
Do I need to cycle a filter before adding fish?
Yes — GEMS need time for bacteria to colonise the ceramic before they're doing useful biological work. Run the filter on an established tank's water, or fishless-cycle with an ammonia source, before adding livestock.
Will GEMS work in a marine tank?
The ceramic itself is fresh and marine safe, but CerMedia markets the Fresh GEMS 50 g pack specifically for freshwater use. For marine or reef systems, the 90 g GEMS box is the one CerMedia rates for marine as well as freshwater.
How long does a box of GEMS last?
Indefinitely, with a periodic rinse. Ceramic biomedia isn't a wear item like filter floss — replace it only if it's physically damaged.
