Water Quality
Phi Anderson from http://www.geocities.com/abear27

Despite the vast abundance of water on the Earth, itis still a very mysterious substance that scientists still do not fully understand. Fortunately for aquarium keeps, basic water chemisty is not too difficult to understand. This page will help you understand why water changes are nexessary, and what characteristics of the water you need to be most concerned about.
Water Changes
Water changes are vital in an aquarium environment. Water changes replace a portion of old water with fresh clean water. This in turn dilutes the concentrations of the undesirable substances that are produced (like nitrates and phosphates), and other chemicals or medications that you may have added to your aquarium. Water changes can cause some stress for the fish. The most important thing is to ensure that temperature and water conditions are equivalent to what you replace. If your fresh water has similar temperature, pH, and GH as your aquarium water, you can easilly change 66% of the tank's water without any harm to your fish. If the water conditions are not similar at all, you can quickly kill every fish in the tank.

Before you put your water in the aquarium, ensure you have removed as many contaminants as possible. This usually means using some kind of aquarium water conditioner. I use a product called Aqua Plus (now also called Aqua Safe), that removes chlorine, chloramine, and neutralizes heavy metals in the water. It also contains what the company calls Pure Herb Extracts that "visibly reduces stress attributed to transportation, handling, and acclimitization...also coats scales and fins to protect against scrapes and cuts." There are a number of these products out there from various manufacturers. They all do about the same thing. The important thing is to use it... if for nothing more than ensuring your fish are not poisoned by chlorine or chloramine from tap water.

For routine aquarium maintenance, you should change 10% to 20% of the water weekly, with a larger 30% to 50% change every month or two. In special situations, you might find you need to do a 30% to 50% water change daily! Water changes are the first line of defence in dealing with many problems, such as disease. You need to be able to do large water changes on short notice. Although you can let your water sit for a few days to disipitate the chlorine, you won't always have that luxury.

Water changes are a necessity for keeping a healthy aquarium. There is no aquarium filter on the market that will remove the wide variety of salts and other chemicals from your tank that you add every day as the by-product of feeding or supplementing the water conditions. A portion of the food you give the fish is not used or bound up by the fish, and ends up being dissolved in the water, increasing water hardness over time. Most freshwater fish usually need relatively soft water, and you need to remove these chemicals from the water in order to keep them healthy in the long term. The only reliable, and proven, way to do this is through regular water changes.

Water Chemistry
You need to know enough about water chemistry to ensure that the water in your aquarium has the right properties for your fish. Beginners typically get fish that are closely matched to the tap water conditions of where they live. To keep other kinds of fish, you need to get control over the water characteristics to make it suitable for them. Water has four properties that are commonly used to characterize the water chemistry in an aquarium: pH, KH, GH, and salinity. These properties interact with each other, and it is often difficult to impact one without influencing the others.

The pH is a measure of the acidity or alkalinity of the water. Water with a pH of 7 is considered neutral, a perfect balance of acidity and alkalinity. Values less than 7 signify acid conditions, while values over 7 indicate alkaline conditions. Tropical freshwater fish tend to like pH values between 6.5 and 7.5, although different species have preferences one way or the other. Fish are extremely sensitive to even small changes in pH. If you do need to start manipulating the pH, monitor it closely, and never expose a fish to changes greater than 0.2 pH per hour.

The Carbonate hardness, or KH, is a measure of carbonate/bicarbonate present in the water. KH is important for the buffering capacity of the water to prevent dangerous shifts in pH. Most freshwater aquariums should have a KH between 2 and 8 dH. Buffering has both positive and negative effects. On the plus side, the nitrogen cycles produces nitric acid (nitrate). Withough the buffering, the pH in the aquarium would drop over time. With sufficient buffering, the pH stays stable. On the down side, hard tap water often has a high buffering capacity, which makes it difficult to lower the pH to an appropriate value.

General hardness, or GH, is a measure of the amount of dissolved calcium and magnesium present in the water. GH tells you if your water is hard, or soft. Water with a GH between 0 and 8 dH is considered soft, 8 to 12 dH is about average, and above 12 indicates hard water. Most freshwater aquarium fish find a GH between 4 and 12 dH acceptable, although different species tend to have preferences one way or the other.

Salinity refers to the total amount of dissolved substances. Salinity measurements include GH and KH components, as well as sodium. Salinity is expressed in terms of specific gravity, the ratio of a solution's weight to the weight of an equal volume of distilled water. You can measure the specific gravity using a hydrometer. Some freshwater fish can tolerate a small amount of salt. Some freshwater fish prefer a small amount of salt in their water. It stimulates slime coat growth and lowers osmotic stress. Many parasites do not tolerate salt at all. Some freshwater fish cannot tolerate salt at all either.

More than 75% of the time, water quality can be traced back as the source of an aquarium problem. Be sure you are doing proper weekly water changes, and that the water conditions are proper for the fish you are keeping!

If you are interested in finding out the details of the water supply where you live, contact your city's Municipal Engineering Department. They do continual checks on the city water supply, and can tell you where the water for the city is supplied from, major ions, general chemical parameters, health related parameters, as well as pesticides and other contaminants.

Water Movement In The Aquarium
The actual movement of water within your aquarium is very important. Without any water movement, there is a layering effect of water temperatures as warmer water rises and cooler water sinks, and there is less water making contact with the surface and thus reduces the efficiency of dissolving oxygen and releasing carbon dioxide in the aquarium. Most fish prefer, and benefit, from a current int the water to swim with or against. Typically, the use of a filter, airstone, and heater create enough water movement in an aquarium to keep the fish happy, the tank temperature uniform, and the surface water contact agitated.

In a large tank, a powerhead could be used to create a current. In some cases, a wave maker can be used to simulate certain ocean conditions.