Keeping a thriving marine aquarium is one of the most rewarding parts of fishkeeping — but success starts with one crucial ingredient: marine salt. It’s far more than just sodium chloride. The right salt mix recreates the complex chemistry of natural seawater, providing your fish, corals, and invertebrates with the essential elements they need to grow, thrive, and stay healthy.
If you’re new to marine aquatics — or simply looking to upgrade your salt — this guide will help you understand the different types of marine salt available, how they work, and how to choose the perfect one for your tank.
Why Marine Salt Matters
In the ocean, thousands of minerals and trace elements naturally dissolve into the water. These include calcium, magnesium, potassium, strontium, and carbonates, among many others — all of which play vital roles in coral growth, pH stability, biological filtration, and fish health.
In a closed aquarium system, those elements need to be replaced manually — and that’s where a quality marine salt mix comes in. When dissolved into RO or RO/DI water, marine salt recreates the exact chemical balance of seawater, ensuring:
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Stable salinity levels for marine fish
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Strong coral skeleton formation (SPS and LPS)
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Balanced pH and alkalinity
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Healthy invertebrate molting and shell growth
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Effective biological filtration
Poor-quality or mismatched salt can lead to unstable water parameters, stress, stunted coral growth, and even livestock loss — so choosing the right mix is one of the most important decisions you’ll make.
Types of Marine Salt Explained
Not all salt mixes are the same. Here’s a breakdown of the most common types and their best uses:
1. Standard Marine Salt – For Fish-Only Systems
If you’re keeping a fish-only tank (FO or FOWLR — fish-only with live rock), a standard marine salt is often sufficient. These blends contain the essential minerals needed for fish health and biological filtration but typically lower levels of calcium and magnesium since corals aren’t present.
Best for: Beginners, fish-only tanks, quarantine systems
Tip: Regular water changes will maintain stable parameters without additional dosing.
2. Reef-Grade Salt – For Coral and Mixed Reefs
Reef-specific salt mixes contain elevated levels of calcium, magnesium, and alkalinity to support coral growth and skeletal development. They’re ideal for tanks containing SPS, LPS, or soft corals, as well as clams and calcifying invertebrates.
Best for: Mixed reefs, coral-dominated tanks
Tip: Look for formulas free from nitrates and phosphates to avoid fueling algae growth.
3. Pro or Accelerated Growth Salt – For SPS & High-Demand Systems
Advanced reef keepers often choose specialised “pro” or “growth” salt formulations. These are designed to deliver high concentrations of key elements, encouraging faster coral growth and vibrant colouration. They’re ideal for high-energy systems with intense lighting and heavy coral stocking.
Best for: SPS-dominant tanks, frag systems, coral propagation
Tip: Monitor parameters closely — these salts are potent and may require additional dosing or adjustment.
What to Look for in a Quality Marine Salt
When comparing salt mixes, consider the following key factors:
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Purity: Choose salts free from nitrates, phosphates, and heavy metals.
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Element balance: Look for mixes that closely match natural seawater (NSW) levels.
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Consistency: Reputable brands deliver stable results batch after batch.
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Ease of mixing: Premium salts dissolve quickly and clearly with minimal residue.
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Compatibility: Some salts are designed for use with RO/DI water and may not perform as well with tap water.
Recommended Parameters for Reef Aquariums
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Parameter |
Natural Seawater (NSW) |
Reef Aquarium Target |
|---|---|---|
|
Salinity |
35 ppt (1.025 SG) |
35 ppt (1.025 SG) |
|
Calcium (Ca) |
~420 ppm |
420–450 ppm |
|
Magnesium (Mg) |
~1280 ppm |
1250–1350 ppm |
|
Alkalinity (dKH) |
~7–8 dKH |
7–10 dKH |
|
pH |
~8.1–8.3 |
8.1–8.4 |
A quality salt mix should bring your tank close to these levels with minimal adjustment.
Tips for Choosing the Right Salt for Your Setup
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For beginners: Start with a high-quality standard marine salt — easy to use and maintain.
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For reef tanks: Choose a reef-formulated or coral-pro salt to support skeletal growth and stable water chemistry.
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For advanced systems: Consider a pro-grade salt designed for accelerated coral growth and higher element demand.
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Stick with one brand: Switching salts can cause parameter swings. If you change, do it gradually over multiple water changes.
Final Thoughts
Choosing the right marine salt is the foundation of a healthy, thriving saltwater aquarium. Whether you’re keeping a simple fish-only system or an advanced coral reef, the right blend ensures stable parameters, vibrant growth, and a stable ecosystem.
At Charterhouse Aquatics, we stock a full range of premium marine salt mixes from trusted brands — suitable for every level of hobbyist. From essential maintenance salts to reef-optimised blends and pro-level coral formulas, you’ll find everything you need to build and sustain a successful marine system.
