What is a water hardness testing kit?

A water hardness testing kit is a kit containing ingredients for measuring the amount or number of grains per gallon of the dissolved salts of magnesium or calcium present in the water.

There are two types of kits available. The first involves the use of three chemicals which are added in succession to a sample of water to be tested. The number of drops of the last solution required to change the color is a measure of grains of hardness per gallon. The second type of kit makes use of the fact that soap will not lather readily in hard water. Drops of a standard soap solution are added to a sample of water. The number of drops required to produce lather equals its hardness in grains per gallon.

A rough idea of the hardness can be gained by washing your hands in some of it. Soft water lathers readily.

Like pH, there is a good deal of controversy as to the practical importance of water hardness. Most fishes can certainly stand extremely hard water if they are gradually accustomed to it. Many fishes will breed much more readily in soft, slightly acid water. There are chemical water softeners which will remove the calcium and magnesium salts from water. There are also water demineralizers available. These remove all the dissolved minerals from the water, leaving it almost as pure as distilled water.

Neither of these should be used on water while the fishes are present. Fishes cannot live in distilled water. To avoid overdoing it, when your water is too hard, make changes carefully. Soften some water separately. Dilute your aquarium water by adding this water to it and testing frequently. The amount to add depends on the degree of hardness you start with and the degree of hardness required. A hardness of 3 to 9 grains of hardness is the most satisfactory, although as stated before most fishes can stand water much harder than this, if the change to it is gradual.

Hardness is frequently measured as parts per million, abbreviated as p.p.m. Divide the number of parts per million by 17.1 to find the grains per gallon.