How to Turn a Freshwater Tank Into a Salt Water Tank

An aquarium full of fish and other wildlife is a simple and relatively easy way to bring animals into your life. Keeping a saltwater tank opens up a realm of new possibilities. Saltwater fish are more colorful than freshwater fish, and there is a greater variety of marine life that can live in saltwater. But saltwater tanks also come with greater challenges, like maintaining the water alkalinity and salinity balances, finding saltwater fish that can coexist and decorating and maintaining the tank. If you want to transition your freshwater tank into a saltwater environment, you can do so with a few easy steps.

Things You'll Need

  • Soft cloth
  • Sump-based filtration system (including protein skimmer, submersible heater, filter sock and return pump)
  • Thermometer
  • Commercial salt mix (available at fish stores)
  • Plastic trash can (at least 20 gallons)
  • Powerhead (submersible pump)
  • Submersible heater
  • RO/DI (reverse osmosis/deionization machine)
  • Substrate (coral, gravel, etc.)
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Instructions

    • 1

      Dump the old water out of your freshwater tank, and clean it with clean water and a soft cloth. Clean your air, pump and filtration systems. Since freshwater doesn't leave any residue, you'll be able to use your old equipment for your saltwater tank without any damage to the new environment.

    • 2

      Set up your equipment, including filtration system and thermometer. Reinstall this equipment in the tank before you put the water in, but do not turn it back on.

    • 3

      Prepare your water in the trash can, so you can prepare more than you need (it's better to prepare more now and have it available for future water changes). Place the submersible pump and heater in the bottom of the trash can to circulate the water. Use the RO/DI to prepare enough water to fill the trash can. Add the salt (available at fish or pet stores) per the manufacturer's directions.

    • 4

      Add the substrate (sand, coral, etc.) to your tank as your base. Add rocks, coral, etc. as desired.

    • 5

      Allow the saltwater to age for 48 hours in the trash can, then add it to your aquarium. Turn on the filtration system and allow it to run for a day as a test. Check for leaks, adjust the temperature, add plants and balance the nitrates and alkalinity at this time. Most saltwater wildlife needs a pH between 8.2 and 8.4. Never let it drop below 8.0. The nitrate reading should be between 5 and 20 parts per million. Take a sample of your water to your local fish store for help in testing it. Your aquarium is now ready for your fish and wildlife.