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How to Correct Marine Aquarium Salinity

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Maintaining a saltwater or marine aquarium takes a bit more diligence than maintaining a freshwater tank. Both tanks should generally have water between 75 and 80 degrees Fahrenheit. However, with a marine aquarium you have to keep an eye on several factors of the water's chemistry. Pick up a testing kit to monitor the water's pH, nitrate, nitrite, ammonia and phosphate levels. Also, watch the water's gravity, or temperature-dependent salinity reading. While most marine life can handle a range of salt content, they need it to remain consistent at whatever level they become accustomed to. Make prompt corrections when necessary.

Step 1

Follow the manufacturer's instructions for the particular salt mix you use when setting up your marine aquarium, and whenever you're adding new water. Use a hydrometer, refractometer or specialty salt monitor to measure salinity. Maintain a constant gravity reading between 1.021 and 1.024. Do not allow changes greater than 0.001 to go uncorrected,

Step 2

Siphon up to 10 percent of tank water at a time and add freshwater in its place to lower the salinity and gravity to the desired levels. Added water should be the same temperature as the aquarium water.

Step 3

Remove up to 10 percent of aquarium water at a time and replace it with salt water to raise the salinity and gravity to the desired levels. Mix the salt water in a large bucket according to the directions and bring it to the same temperature as the tank water before adding it.

Step 4

Change the marine aquarium's gravity by no more than 0.001 in a day. A greater change in either direction can cause shock or death to aquarium inhabitants. Correct salinity gradually over the course of a few days if necessary.