Basic Aquarium Water Parameters
Here's an introductory description of the most important water parameters for the aquarium hobby.
- pH (Power of Hydrogen)
pH is the measurement of hydrogen ions. Increased hydrogen ions (less bonding) result in a drop of the pH (more acidic water), while a decrease results in a pH rise. pH is measured on a scale from 0-14. The neutral value is 7, while values below are more acidic (towards a car battery) and values above 7 more basic (towards dish soap). Changes in pH are a common cause of fish fatalities. Fish can adapt to most pH levels, if not broadly out of range, but they don't adapt well to bouncing values. This is because pH has a logarithmic function (mathematical - meaning ten-fold). In other words, a change in pH from 7 to 6 means 10 times more acidic water. A further drop to a pH of 5 equals 100 times more acidic water. If you have to adjust the pH in your tank, always consider the carbonate hardness (below). The pH in harder water is more difficult to adjust because it bounces back, while softer water is more easily adjusted. Keep in mind to change it slowly as it causes a lot of stress to your fish. Maintaining a stable pH is generally more the way to go.
Some other facts about pH:
- Ammonia increases in toxicity with rising pH
- Nitrifying bacteria experience reduction of growth and action below a pH value of 6
- Water Hardness
- Nitrogen Compounds
Ammonia, Nitrite, Nitrate are well described in The Nitrogen Cycle article.
Phosphates enter the aquarium mostly through water changes using tap water, but also through food and leaching carbon. Next to chlorine some communities also add phosphates to the tap water. Dying plants and algae will create phosphates while decaying (mineralization). Very interesting to know is the fact that the high pH level required for salt water will hold phosphates in an insoluble stage. A drop in pH, and this happens in a matter of days, will make those compounds water soluble and therefore available to the algae spores. Note that the pH levels usually vary slightly within the tank, and a drop in one spot can have an effect.
The most common points of entry are the substrate, salt, water and dying diatom algae. Keep in mind that R/O and DI units (filters to purify tap water by membranes or by chemical/mechanical processes creating distilled water) will prevent silicates only for a few days, before they find the way through the membranes. Another form of silicates is silicid acid, created by decaying organic matter. Same as phosphates, they can be water insoluble at a high pH, and become readily available with decreasing pH levels.
Water companies add chlorine or chloramine as a disinfectant to tap water. Chlorine is less stable then chloramine and airs out in just a few days. Some hobbyists simply let the water age for a couple of days before doing the water change, thus airing out the chlorine. Chloramine is much more stable. That is why communities switch from chlorine. As it is very stable, it does not air out even if heavily aerated. Chloramine, a mixture of ammonia and chlorine, passes (unlike chlorine) through the fish’s tissue directly into the bloodstream. In the blood, just like nitrite, it destroys the oxygen carrying cells. Chloramine can cause all fish to die within 24 hours.
Carbonate hardness, pH, nitrate, and ammonia/nitrite (salinity for marine tanks), should ideally be tested on a weekly basis. Also be sure to test the water used during water changes.
The water parameters and definitions in this issue are intended to help you understand the conditions in your aquarium. A healthy aquarium requires immediate attention should one of these parameters produce dangers readings.
Other parameters such as trace elements i.e. iron, copper, calcium etc. should be checked on, if you add them in some way (as supplement or fertilizer).
Depending on the set up (marine/reef/plants), other factors come in to play, such as dissolved oxygen, redox potential or CO2. These topics will be covered in future issues regarding specific tank types.
First of all, I am a great fan of your website. Therefore this 'tiny' little improvement (or perfection): pH meaning 'power of hydrogen' is only a general assumption (due to a translation from the German word 'potenz'). Which is also a misconception. The H of course stands for the H+ ion, but the little p was merely a convention used by its inventor Sorenson, so it doesn't really have a meaning. My proposal is to call pH 'acidity or alkalinity' (or equal correct explanation) for a more scientific correct approach. Reference: http://www1.umn.edu/ships/words/pH.htm for completeness.
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