An essential calcium supplement for any invertebrate keeper. Our 100g bag of crushed oyster shell provides a natural, long-lasting source of calcium carbonate along with trace minerals including magnesium, sodium, iron, strontium, and other micro-elements. Calcium is one of the most important nutrients you can offer your invertebrates — without it, exoskeletons weaken, moults fail, and shells deteriorate. A 100g bag will last most keepers a long time, as only a small amount is needed per enclosure.
Why Crushed Oyster Shell?
All arthropods and molluscs rely on calcium to build and maintain their protective outer structures. Isopods, millipedes, snails, and crabs all undergo regular moulting or continuous shell growth, and each of these processes demands a reliable supply of calcium. Crushed oyster shell is one of the best ways to deliver it — it breaks down slowly, won't foul your enclosure, and unlike egg shells, it doesn't attract mites. Your invertebrates will use their mandibles to gradually break down and consume the shell fragments over time, giving them a steady, sustained source of calcium between top-ups.
Which Invertebrates Benefit?
Crushed oyster shell is a versatile calcium source that benefits a huge range of species commonly kept in the hobby:
Isopods (All Genera)
Calcium is critical for all isopods. As terrestrial crustaceans, they have a chitin-and-calcium-carbonate exoskeleton that is shed regularly as they grow. Without adequate calcium, moults can fail and exoskeletons become soft and deformed.
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Armadillidium – Roly-poly species like A. vulgare, A. maculatum (Zebra), A. klugii (Clown), and A. gestroi have thick, domed exoskeletons that demand high calcium intake. These species in particular benefit from having crushed oyster shell consistently available.
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Porcellio – Active, fast-growing species such as P. scaber, P. laevis (Dairy Cow), P. ornatus, and the larger Spanish species like P. expansus, P. hoffmannseggi, and P. bolivari moult frequently and need a reliable calcium source to keep up with their rapid growth.
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Cubaris – Premium species like Rubber Ducky, Panda King, and other Cubaris varieties need calcium to support healthy moulting and colony development, especially given their slower reproduction rates.
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Porcellionides – Powder isopods (P. pruinosus morphs) breed rapidly and moult often, making a constant calcium supply essential to sustain fast-growing colonies.
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Ardentiella (ex Merulanella), Cristarmadillidium, Oniscus, Venezillo, Trachelipus, Troglodillo & others – Every isopod genus in the hobby benefits from supplemental calcium. It should be treated as a non-negotiable staple in every enclosure.
Millipedes
Millipedes have a hardened, calcified exoskeleton made up of dozens of segments, and they add new segments with every moult throughout their lives. Calcium deficiency is one of the most common causes of weak, pitted, or deformed exoskeletons in captive millipedes. Species like the Giant African Millipede (Archispirostreptus gigas), Spirostreptus, and other commonly kept genera will readily consume crushed oyster shell mixed into their substrate. In the wild, millipedes actively seek out and chew on calcium-rich rocks and mineral deposits — crushed oyster shell replicates this in captivity.
Giant African Land Snails (GALS) & Other Land Snails
Snail shells are made almost entirely of calcium carbonate, so calcium supplementation isn't optional — it's essential for survival. Without it, shells become thin, pitted, cracked, and prone to breakage. Crushed oyster shell can be mixed into the substrate or offered in a shallow dish, and snails will actively seek it out. It works brilliantly as an alternative or complement to cuttlebone for all land snail species including Achatina, Lissachatina, Cornu, and garden snail species.
Hermit Crabs
Hermit crabs rely on calcium for healthy exoskeleton development and successful moulting. Crushed oyster shell is one of the most commonly recommended calcium sources in the hermit crab hobby — many keepers find their crabs consume it more readily than cuttlebone. It can be offered in a dish or mixed into the substrate.
Cockroaches & Beetles
Dubia roaches, hissing cockroaches, and other feeder or pet roach species benefit from calcium supplementation, particularly breeding females. Beetle larvae and adults with calcified exoskeletons also benefit from having oyster shell available in their substrate.
How to Use
For isopods: Sprinkle a small amount into the enclosure — either directly onto the substrate surface or in a food dish. Top up as it gets consumed, typically every few weeks.
For millipedes: Mix into the substrate so your millipedes can graze on it as they burrow. You can also place small piles on the surface near feeding areas.
For snails: Offer in a shallow dish or mix into the top layer of substrate. Snails will find it and consume it as needed.
For hermit crabs: Place in a calcium dish within the enclosure alongside other calcium sources.
What You Get
100g of 100% natural crushed oyster shell. No additives, no chemicals — just pure, clean oyster shell.
