Start with two equal-sized containers—the Seachem Just Add Water 5 Gallon Water Jug TWO PACK works well— , and fill one with RO/DI water. The second jug will be used to collect the water removed from the aquarium. As the jugs are of equal size, it will be easy to determine that the amount of water removed is equal to the amount returned to the aquarium.

You can purchase water from your local fish store or make your own using an RO/DI unit. We recommend the AquaticLife Twist-In Compact 4-Stage RO/DI Unit.

Add salt to the RO/DI water in your mixing container. We recommend Two Little Fishies AccuraSea1 Artificial Saltwater Mix. This 50-gallon size has ten packets of salt that each make 5 gallons of saltwater. These five gallon packets are the perfect size for the Seachem Just Add Water 5 Gallon Water Jug.

Place a small pump like a Lifegard Aquatics Quiet One Pro Model 400 Pump in the jug and plug it in.

Wait for the salt to mix. Different salt manufacturers have different recommendations for how long to mix salt. We recommend eight hours. Starting the pump before you head off to a full day of work or before bed will ensure the water is ready when you return.

We have a package that combines the recommended products called the Two Little Fishies Small Saltwater Aquarium Salt Mixing & Water Change Package. It combines the Seachem Just Add Water 5 Gallon Water Jug TWO PACK, Lifegard Aquatics Quiet One Pro Model 400 Pump and the Two Little Fishies AccuraSea1 Artificial Saltwater Mix.

Use a hydrometer or refractometer to confirm the salinity of your new saltwater, and adjust if needed. We use and recommend the MarineAndReef.com Reefractometer and the Coralife Deep Six Hydrometer. Refractometers are more expensive but more accurate and last much longer than hydrometers.

Turn off all of the aquarium equipment except the light.

Use a gravel vac like a Python 25 ft. No Spill Clean & Fill Gravel Vac or a Python Extended Length Gravel Tube to drain the dirty tank water into your empty jug (or jugs). The Python Squeeze Stressless Siphon Starter can make starting the siphon much easier. We sell these two products together at a discount as the Python 25 ft. No Spill Clean & Fill and Squeeze Stressless Siphon Starter Package.

Add RO/DI with correct specific gravity back to your aquarium.

Turn back on your aquarium equipment.