For instance, rain from chalky areas near the coast often have higher than normal levels of calcium caused by the chalky soils in these areas. As we are all aware, atmospheric pollution can have a major effect on the composition of rainwater, typically caused by heavy metals such as lead, zinc or chromium from industrial processes, although such effects are more likely to be local, not widespread. These gases can react with rain to form strongly acidic solutions, giving acid rain. Some parts of the world, including the UK have recorded pH values as low as 2.1, due to acid rain. Some fish keepers outside the UK have started to cover their ponds to protect them from acid rain.
Rain picks up significant amounts of nitrogen, sulphur and sodium in the atmosphere.
At this stage it is likely to be very soft. Without going into details at this stage, let me advise that you do not collect soft acidic rain for fish pond water changes. Rock weathering Most of the inorganic substances in tapwater come from rock weather ing. As the nature of the local rock varies, so does the content of the local water. The degree and rate of rock weathering depends on several factors.