Marine Aquarium Salt & Reef Salt
Discover premium marine aquarium salt and reef salt at Rock ’N’ Critters, including trusted formulations from Red Sea, Fauna Marin and Aquarium Systems.
Whether you're setting up a new marine aquarium, preparing regular water changes or maintaining a demanding SPS coral reef, choosing the right salt mix is essential for stable water chemistry.
Our range includes everyday marine salts, enriched reef salts and professional formulations with carefully balanced calcium, magnesium, alkalinity and trace elements.
Shop Instant Ocean, Reef Crystals, Red Sea Salt, Coral Pro and Fauna Marin Professional Sea Salt, available in a selection of practical sizes and packaging options.
Find the right salt for your aquarium and maintain the water chemistry your marine life depends on.
Browse our full marine salt range below:
Choosing the Best Marine Salt for Your Aquarium
Not all marine aquarium salts are formulated in the same way. Different salt mixes provide varying levels of alkalinity (KH), calcium, magnesium and trace elements, making some better suited to particular reef-keeping approaches.
At Rock ’N’ Critters, we stock a carefully selected range of marine salts for everything from fish-only systems to demanding SPS coral aquariums.
Which Marine Salt Should You Choose?
Aquarium Systems Instant Ocean Sea Salt
A dependable, versatile marine salt for fish-only, FOWLR and mixed reef aquariums. Its balanced formulation and everyday value make it ideal for regular water changes and larger marine systems.
Aquarium Systems Reef Crystals Sea Salt
An enriched alternative to Instant Ocean, formulated with elevated calcium, magnesium, additional trace elements and vitamins. An excellent choice for mixed reefs and coral aquariums requiring enhanced foundation elements.
Fauna Marin Professional Sea Salt
A premium, laboratory quality-controlled reef salt with balanced, natural seawater-like chemistry. Particularly suitable for SPS, LPS and mixed reef aquariums where consistent parameters are a priority.
Red Sea Salt
A premium marine salt with moderate alkalinity of approximately 8 dKH, balanced calcium and magnesium, and naturally derived ingredients. Particularly suited to SPS-dominated reefs and aquariums maintained near natural seawater alkalinity.
Red Sea Coral Pro Salt
A high-alkalinity reef salt formulated with elevated calcium, magnesium and approximately 12 dKH alkalinity. Ideal for mixed reefs, coral growers and frag systems deliberately maintained at higher alkalinity.
Understanding Calcium, Magnesium & Alkalinity
Alkalinity (KH) helps maintain stable reef water chemistry and supplies bicarbonate for coral calcification.
Calcium is essential for the formation of coral skeletons, coralline algae and other calcium carbonate structures.
Magnesium helps maintain the chemical balance between calcium and alkalinity in seawater.
When choosing a salt, look for a formulation that closely matches your aquarium's intended water parameters. Higher levels are not automatically better, particularly when changing salt brands.
How to Mix Marine Aquarium Salt
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Start with clean, purified RO/DI water.
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Add your chosen marine salt gradually while circulating the water.
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Follow the manufacturer's mixing instructions.
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Measure salinity with a calibrated refractometer or salinity meter.
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Match the temperature and salinity of your aquarium before use.
For many tropical reef aquariums, a salinity of approximately 35 ppt is commonly maintained.
Always add salt to water, never water to a container of dry salt.
Complete Your Water Change Equipment
For reliable saltwater preparation, consider pairing your chosen marine salt with RO/DI water, a refractometer, a suitable mixing pump and aquarium water test kits.
Need Help Choosing?
Not sure which salt best suits your aquarium? Contact the experienced team at Rock ’N’ Critters in Barry, South Wales, for advice on marine salt selection, reef water chemistry and aquarium maintenance.
The right salt, stable water chemistry and consistent maintenance provide the foundation for a successful marine aquarium.