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CALCULATING HOW MUCH SALT TO ADD

PPM is a measure of concentration in water. You cannot weigh ppms. However, 1 mg/l is almost the exact equivalent in water to 1 ppm. So one can use ppm and mg/l interchangeably in this case. You can weigh milligrams.

To add 10 mg/l of chloride for every ppm of nitrite in the water, use the following steps:

1. Multiply your nitrite test reading by 10. This will give you the needed mg/l of chloride you need to add.

2. Calculate the actual volume in litres of the water in your tank. If your volume is in gallons you must convert this into liters. (As a rule, using the advertised volume of the tank at about 85% will put you in the right ballpark.) 1 gallon = 3.875 litres

3. Multiply the number in #1 above by the number of liters of water in #2 above to get the total number of mg of chloride you will need to add.

4. Because salt is roughly 2/3 chloride, you must multiply the number calculated in #3 by 1.5. You now know how many mg of salt you should add to the water. Dividing this number by 1,000 will convert this amount to grams which are easier to weigh for most people.

5. Do not add the dry salt directly to the tank. Remove some tank water to a container and mix the salt in that, then add the salt water to the tank spreading it around the surface.

Hint: We have calculated a handy conversion from grams to volume so one can measure in tea or table spoons which most folks are likely to have while a gram scale is not. The following calculations were made using an Ohaus triple beam scale: ¼ teaspoon of salt shaker sized table salt weighs 2 grams.

The readings used in this article are for API and similar type test kits which measure in total ions. Some kits will measure using a different scale, they are only measuring the nitrogen ions. You can tell when a kit reads just the nitrogen ions by the way they state things. The typical kits will say they measure Total Ammonia (NH3 + NH4), Nitrite (NO2) or Nitrate (N03). Kits that measure only the nitrogen ions will usually say they measure Total Ammonia-Nitrogen (NH3-N + NH4-N), Nitrite-Nitrogen (NO2-N) or Nitrate-Nitrogen (NO3-N).

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