How to Mix Reef Salt Correctly for Your Aquarium

The Complete Guide for Marine & Reef Tank Enthusiasts

Whether you’re setting up a new reef tank or performing routine maintenance, knowing how to properly mix reef salt is essential for maintaining stable, healthy marine water conditions. In this step-by-step guide, we’ll walk you through everything you need to know — from choosing the right salt to achieving optimal salinity and ensuring a stress-free environment for your corals and marine fish.

Why Mixing Reef Salt Correctly Matters

Marine aquariums are delicate ecosystems where consistency is key. Incorrectly mixed saltwater can lead to:

- Fluctuating salinity levels

- Undissolved particulates that stress corals

- Unstable alkalinity and calcium levels

- Algae blooms due to impurities

By mixing your reef salt properly, you ensure water quality that supports vibrant coral growth, proper osmoregulation for fish, and long-term tank stability.

What You Need to Mix Reef Salt Properly

Before you start, gather the following tools and materials:

Step-by-Step: How to Mix Reef Salt Safely

1. Fill Your Mixing Container with RO/DI Water

Use only high-purity water from a reverse osmosis (RO) or RO/DI system. Fill your container with the amount of water needed for your upcoming water change or tank top-up.

2. Heat the Water to the Target Temperature

Use a submersible heater to bring the water to 75–78°F (24–26°C). Temperature affects salinity readings, so it’s vital to match the tank conditions.

3. Weigh and Add the Reef Salt

Using a digital scale, weigh your salt according to the manufacturer’s instructions. Most reef salt mixes recommend:

• 35 grams per litre to achieve 35 ppt salinity

Add salt slowly and gradually, allowing time for each portion to dissolve before adding more.

4. Mix with Circulation

Place a powerhead or circulation pump in the container to thoroughly mix the salt. Let it run for at least 2–4 hours, or until the solution is completely clear.

5. Measure and Adjust Salinity

Use a calibrated refractometer or digital marine salinity tester to check your final salinity.

- Target: 35 ppt or 1.025 specific gravity

If the salinity is off:

• Add more salt to increase salinity.
• Add more RO/DI water to lower it.

6. Let It Rest (Optional, But Recommended)

Let the water sit for a few hours, ideally overnight, to stabilize. This also gives time for the pH and temperature to settle before use.

Storing Mixed Saltwater

You can store pre-mixed saltwater for up to 5–7 days if it’s kept in a clean, sealed container and circulated regularly. Avoid using it if it smells bad or shows signs of bacterial growth.

Common Mistakes to Avoid

- Using tap water – leads to unwanted chemicals, algae, and instability.

- Guessing salt amounts – always weigh, never estimate.

- Skipping salinity checks – every batch should be tested.

- Mixing in cold water – this can cause precipitation of calcium and magnesium.

Recommended Reef Salt Brands (Available at Charterhouse Aquatics)

- Red Sea Coral Pro Salt – high calcium, ideal for SPS coral tanks.

- Tropic Marin Pro Reef – balanced formula, excellent for mixed reefs.

- Instant Ocean Reef Crystals – budget-friendly and widely trusted.

- AquaForest Reef Salt – premium blend with trace elements.

Final Thoughts

Correctly mixing your reef salt is one of the most fundamental — yet often overlooked — practices in marine aquarium care. With the right tools and a little patience, you can ensure each water change supports a thriving, stable reef system.

Still have questions?

Visit our Help Centre or contact our marine team at Charterhouse Aquatics — we’re here to help you every step of the way.