Mixing Artificial Seawater

From RTAW Reefpedia

Introduction

Artificial seawater needs to be mixed before use in a separate container. Do not add salt directly to the aquarium. It is preferrable to use RO, DI or RO/DI purified water to make up the ASW.

Add the salt to the water, rather than water to the salt. In order to minimise precipitation of solids from the mix, it is best to start with the appropriate amount of freshwater required and slowly add salt mix to this while mixing, until the required specific gravity is achieved.

Procedure

1. Add the required freshwater to the mixing container.
2. Add around one quarter of the required salt to the water.
3. Mix the salt and water thoroughly until solution is clear.
4. Add another quarter of the required salt to the water.
5. Mix the salt and water thoroughly until solution is clear.
6. Add another quarter of the required salt to the water.
7. Mix the salt and water thoroughly until solution is clear.
8. Check the specific gravity of the solution.
9. Add a small amount of salt to the solution.
10. Mix the salt and water thoroughly until solution is clear.
11. Check the specific gravity of the solution. Repeat steps 9-11 until the required specific gravity (1.025-1.027) is achieved.
12. Heat the water to the desired temperature

While not necessary, it is helpful to aerate the mixed water before use.

Resources

• The toxicity of some freshly mixed artifical seawater - by Ron Shimek.
• How to Mix Artificial Seawater The “How To” Guide to Reef Aquarium Chemistry for Beginners, Part 1: The Salt Water Itself - reefkeeper.com