Soft Water And How To Achieve It.
By Jim E. Quarles
22-04-99

For those who keep and spawn discus and other Amazon fishes the need for soft water, should be second nature to them, but the battle starts with your efforts of achieve this objective.

THE QUESTION?

How may hard water be softened?
The answer! One may have a better perspective of how to soften hard water if they understand just what water hardness means.

The term hardness relates to the concentration of ions having a positive electrical charge of two, called divalent ions. Examples are calcium ions and magnesium ions. Removing the divalent ions will soften the water.

Hydrated salts such as table salt ( sodium chloride ) is in a solid state and the ions are tightly bonded to each other. When dissolved in water, they become electrically charged: they become loosely attracted to each other. This allows the ions to exchange electrons in random order. When an element or compound is electrically charged it is said to be ionized.

There are various ways by which water can be softened, namely ( 1. distillation, 2. reverse osmosis, 3. deionization, and 4. peat filtration).

DISTILLATION:

When water is heated to a boil only the water molecule H20 evaporates. Calcium and magnesium ions are left behind in the heating container. When steam is directed to a cold area, it condenses and becomes pure water. It is as soft as water can become at that point. To restore osmotic balance to the water, some mineral salts need to be added back to the softened water before it can be life sustaining.

The disadvantage to this method of water purification is the prohibitive cost of energy to heat the water.

Both saltwater and freshwater fishes cope with the concentration of salts and dissolved solids in water by a process called osmotic balance. The cells of the freshwater fish are Salter then their ambient water. By diffusion, water constantly enters the body of the fish. The membrane of the fish has the ability to pump the water out in order to maintain its salt content.

When the pressure of the water entering the body is greater than can be pumped out, the fish will die. One the other hand sea water is saltier then the tissues of the fish. The fish has to constantly drink water, or die of dehydration. Excess ions taken in along with the water are carried in the blood and excreted at the gills.

Reverse osmosis:

Reverse osmosis involves the application of a semi permeable membrane where pressure is higher on one side then the other. The pores or openings of the membrane are so fine that only water molecules, ( H2O ) can pass through. Calcium and magnesium, being larger than water molecules, are trapped. The water that has passed through reverse osmosis is almost pure.

The shortcoming of this method of purification is that a very large volume of water is wasted since it must be discharged from the system.

I might also point out that this method of purification requires that the source water be under pressure in order to work properly or on a scale large enough to be of any value.

Deionization:

Deionization is the purification of water by the application of chemical substances called resins. There are two types of resins: anion resins which remove negatively charged ions such as chloride, and Cation resins which remove positively charged ions such as calcium. Synthetic resins remove electrically charged elements or compounds from water and exchange it with something else. In this process the ph of the water under goes a radical change, and close attention is needed. Be prepared to correct the ph. level before it drops to the danger zone for your particular fish in the tank.

Peat moss:

Dried peat moss acts as natural deionizer. There is an exchange of ions when water passes through it. It can be used and become cost effective. However, organic matter such as tannic acid is added to the water causing discoloration. This may be mitigated by the use of activated carbon. The disadvantage is that it is messy to work with, and must be replaced after it loses its ability to acidify / soften the water.

A note to those who keep discus fish. These fish are found only in soft acidic water in nature. A hobbyist should care enough to provide the same or should not keep this fish.