How To Keep Water Quality High in Garden Ponds – Part Two

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by James Lawrence
(West Islip, NY, USA)

If you missed part one please CLICK HERE to return to read part one of “How To Keep Water Quality High in Garden Ponds”

The Acidity of Water

The degree of acidity of water is expressed in terms of a pH value. A pH of 7 represents neutral water. Anything below (0 to 6.9) indicates acidic water, and anything above (7.1-14) indicates alkaline water.

The proper pH range at which fish thrive is either 6.5 to 7 (slightly acidic) or 7.1 to 8.5 (slightly alkaline). Water with a pH of less than 6 can endanger the fish.

The pH of a pool can fluctuate somewhat in the course of the year and even in the course of a day as a result of weather and plants. This is normal and does not harm the fish.

You should measure the pH of the pool water from time to time. Heavy downpours, for instance, can affect the pH adversely. Measuring the pH is especially important in the fall when great masses of dry leaves may suddenly blow into the pool. As bacteria break down the leaves, they release humic acid, which quickly lowers the pH value to around 5 and less. This means death for most fish.

The pH must be corrected if it deviates from the levels required by the fish. Immediately change a third of the water. Repeat if necessary.

The Nitrite-Nitrate Concentration

Since a proper nitrite-nitrate concentration is extremely important for the well-being of the fish, you should definitely check it regularly.

You do not have to be a chemist to do the checking (the procedure is simple), but you should have some understanding of what is involved. Chemical processes are continually going on in the water of a pool as bacteria break down organic plant and animal tissue (wilting and dead plant parts, fish excreta, other animals, food remains).

In the course of this breakdown activity nitrite (N02) is produced, which is poisonous for fish. The nitrite is in turn changed into nitrate (N03), which is not harmful to fish. In this process oxygen is withdrawn from the water. As long as plenty of oxygen remains in the water and not too many waste products are present, this cyclical process functions fine. When the nitrite-nitrate concentration remains low enough, it does not interfere with the well-being of the fish.

Too high a nitrite-nitrate level is harmful not only to the fish but to the entire pool. The excess of nutrients stimulates increased algae growth. A high nitrite concentration causes poisoning symptoms in the fish, and the shortage of oxygen drives them to the water surface, where they gasp for air.

Preventive measures are especially important in ornamental pools that contain fish. There you should definitely change a third of the water every three weeks and be careful to feed the fish properly. A very effective way to prevent a nitrite-nitrate imbalance is to set up a stream that will act as a biological filter.

An emergency measure, especially if your fish are already gasping for air at the surface, is to change a third of the water immediately and add a water restorative to the pool (follow instructions for use!).

Water Hardness

The amount of mineral matter, such as calcium and magnesium, in the water determines its degree of total hardness. Total hardness is measured in parts per million or degrees of dH (dH stands for deutsche Harte, which means German hardness). Usually, water is classified as soft, 100 to 150 parts per million (4-8 dH); medium-hard, 150 to 300 (8-17 dH); and hard, 300 to 535 (17-30 dH).

Most pond fish thrive in medium-hard water, and some also do well in water that is harder than that. Generally, the hardness of tap water is acceptable.

You can find out how hard your tap water is by calling your local water company, or you can measure it yourself with a test kit.

Important for Measuring Water Hardness: It is the carbonate hardness that counts, that is, the amount of calcium and magnesium that is combined with carbonic acid. The carbonate hardness determines to what extent fluctuations in the pH are buffered so that they will not reach extreme levels that would be fatal to many organisms. The carbonate hardness is part of the total hardness and is measured separately from the latter with a chemical test kit.

If you missed part one please CLICK HERE to return to read part one of “How To Keep Water Quality High in Garden Ponds”

Updated: December 18, 2013 — 6:39 am

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