Water Changes - Probably the most dreaded part of successful fish keeping. Often the frustration of improper water parameters leads to the common error of infrequently changing large amounts of water in order to fix the problem.
Proper filtration is essential, but can not remove all the trace elements that accumulate within the water column. Keep in mind that only pure water evaporates while water changes will remove pollutants and replenish diminished elements (calcium, potassium, iron, zinc) necessary for a balanced aquarium.
Under normal conditions a water change of 10% weekly or 15-20% every other week is sufficient. The amount of water to be changed greatly depends on the overall water quality and the bioload. Declining water parameters can often be improved by more frequent changes.
Remember that BIG changes require BIG adjustments (for your overall biological balance). Large water changes of 50% and more will in many cases not improve anything but cause more problems.
Changing water can be a lot more pleasant when done more frequently with smaller amounts. Consider changing the water weekly or once every 2 weeks simply by vacuuming the gravel and replacing the extracted water. Vacuuming the gravel will remove particulate, which otherwise decays, creating pollutants such as ammonia and nitrates.
- WATER temperature should be +/- 5 degrees F of the tank water
- WATER should be free of chlorine/chloramine and heavy metals (lead, copper)
- NEVER use hot water to adjust the temperature. It will shock the fish and older hot water tanks sometimes contain toxic levels of zinc
- IF TAP water is used, let the water run for a minute to clear the lines of possible dirt particles
Watch for what you're putting in your tank! If your using tap water check it for nitrates, but more importantly for pH and kH to be sure it meets the needs of your aquarium.
Also be sure the water you add is about the same temperature as the water in your aquarium before adding it. Extreme temperature changes can be very harmful for your fish.