Complete Guide to Making Artificial Saltwater | Brand Comparison and Correct Dissolution Method

In the care of marine fish and corals, the quality of artificial saltwater and correct preparation methods form the foundation of aquarium environments. Artificial saltwater solutions modeled after natural seawater are sold by multiple manufacturers, each with their own characteristics and strengths. By dissolving according to correct procedures and adjusting to appropriate specific gravity, you can create a safe and comfortable environment for your aquatic life. This article provides detailed explanations from the basics of artificial saltwater to brand comparisons and accurate methods of preparation.

Basics and Components of Artificial Saltwater

Natural seawater contains approximately 35g/L of salt, in which over 60 types of elements are dissolved including sodium, chlorine, magnesium, calcium, potassium, and strontium. Artificial saltwater powder is a blend of these components in powder form, and can recreate seawater with a composition close to natural seawater simply by dissolving it in tap water. A specific gravity of 1.023–1.025 (salt concentration approximately 33–35g/L) is the appropriate range for rearing marine fish and corals. Artificial saltwater is broadly divided into "fish-only types" and "high-function coral types."

• Fish-only types contain basic salt and minerals at an affordable price.
• Coral types are adjusted to higher levels of calcium, magnesium, and trace elements than natural seawater, with strengthened components necessary for coral skeletal formation and coloration.

Choose based on your aquatic life.

Comparison and Selection of Major Brands

Here is a comparison of major artificial saltwater brands available in Japan.

An important point in choosing brands is to avoid changing your chosen brand as much as possible. Frequently changing brands can cause fluctuations in trace element balance, potentially stressing sensitive corals.

Correct Dissolution Procedure for Artificial Saltwater

The procedure for making artificial saltwater is as follows.

1. First, prepare the required amount of dechlorinated tap water (RO/DI water is ideal) in a bucket or water container. Adjust the water temperature to around 25°C. With cold water, alkaline components may not dissolve completely, and with water that is too warm, some components may undergo chemical changes.
2. Next, add the prescribed amount of artificial saltwater powder. For typical products, this is approximately 330–360g per 10L of water, but always follow the package instructions.
3. Stir with a powerhead or aeration and allow to dissolve completely. Dissolution may take 30 minutes to several hours.
4. Once completely dissolved, measure the specific gravity with a hydrometer. The target is 1.023–1.025; if it's low, add a small amount of artificial saltwater powder; if it's high, add freshwater to adjust. Since specific gravity changes with water temperature, it is important to measure at the same temperature as your aquarium. A refractometer is most accurate, and floating hydrometers are not recommended due to large margins of error.

The prepared seawater can be used immediately, but allowing it to sit for 24 hours with aeration will make the components more stable.

Using Artificial Saltwater During Water Changes

Regular water changes are essential for maintaining the health of marine aquariums, and this is where correct use of artificial saltwater is critical. A guideline for water change frequency is 10–20% weekly for fish-only aquariums, and 10–15% every two weeks for coral aquariums. Prepare the water for water changes the day before and adjust it to the same temperature as your aquarium. If there is a temperature difference of 1°C or more, it will stress your aquatic life, so use a heater to match the temperature. The procedure for water changes is to first drain the aquarium water using a hose, then while stirring the substrate surface, also siphon out any detritus (accumulated organic matter) that has settled to the bottom. Next, slowly pour in the prepared new seawater. Using a drip line for slow water addition will minimize rapid changes in water quality. After the water change, recheck the specific gravity and make fine adjustments if necessary. If the specific gravity has risen due to evaporation, it is efficient to add RO/DI water before the water change to return the specific gravity to the appropriate level before performing the water change.

Comparison and Practical Use of Natural Seawater

Natural seawater is seawater collected directly from the ocean and contains trace elements, plankton, and bacteria that cannot be fully replicated in artificial saltwater. The advantages of natural seawater are that it is water with natural balance, and there are reports that it has particularly positive effects on coral coloration and growth. Ideally, clean seawater should be collected from offshore, away from the coast; seawater near harbors or river mouths should be avoided due to contamination and fluctuations in salinity. The disadvantages of natural seawater are that water quality varies depending on the collection location, there is a risk of parasites and pathogens being introduced, and the effort of transporting large quantities of seawater is required. Some aquarists in urban areas use natural seawater delivery services. As a practical guideline for use, a well-balanced approach would be to perform regular water changes with artificial saltwater and use natural seawater once a month during water changes. When using natural seawater for the first time, it is safer to perform water changes at approximately half the normal volume, confirm your aquatic life's response, and gradually increase the amount.

Tips for Preparing and Storing Artificial Saltwater

Creating artificial saltwater at the correct concentration requires several important points. First, always use RO/DI water (pure water purified through reverse osmosis membrane). Tap water contains chlorine, heavy metals, silicates, and phosphates, which negatively affect fish health and algae growth. Place RO water in a bucket or storage container, add the prescribed amount of artificial saltwater powder, and stir well. Stir with a powerhead or aeration for at least 30 minutes to 1 hour, and use only after completely dissolved.

Before using the prepared artificial saltwater, always check the specific gravity (1.023–1.025 with a refractometer), water temperature (same as your main aquarium), and pH (8.0–8.4). Pre-prepared saltwater can be stored in an airtight container with aeration for approximately one week. When preparing large quantities in advance, it is convenient to place a heater and pump in a bucket or storage container and circulate it so it is ready to use whenever needed.

Start Marine Fish Keeping with BreederDirect

Correct preparation of artificial saltwater is a fundamental skill for marine fish keeping. On BreederDirect, you can directly ask marine fish and coral breeders about the brands of artificial saltwater they use and their management methods. Reference the practical know-how of breeders as you work toward creating a stable marine environment.