Tap or well water are still far from perfect pond waters
In most cases tap water is intended to be suitable as drinking water for us humans. It needs to be germ-free – nothing else. In some regions it contains a lot of minerals (hard water), whereas in others very few (soft water). Because of the water pipes it can contain heavy metals, such as copper, lead or zinc which can be toxic for our water dwellers. In some countries and regions chlorine is added for its disinfection. No water animals can easily tolerate chlorine.
The copper rain gutter problem
If you direct rain water through copper rain gutters into your pond, the following happens: The rain water dissolves copper from the copper gutter and it enters your pond. Copper is not only a problem for invertebrates, it can also be deadly for fish from a concentration of 0.3 mg/l.
That’s why a water conditioner JBL BiotoPond is highly advisable. It neutralises the effect of chlorine and encloses (chelates) heavy metals so that they no longer pose a problem.
In regions with soft water and whenever rain water enters the pond, the mineral content of the water decreases steadily. One part of the minerals, the so-called carbonate hardness, ensures a stable pH value. If its content drops too, the pH level of your pond is no longer stable and fluctuates wildly. Since the pH value has a logarithmic scale, a rise from 7 to 10 in the course of the day means a thousand fold decrease of the acid components in the water. At night the pH value drops again and the animals again have to cope with a thousand fold increase of the acid components. You don’t have to be a biologist to see that this not good in the long run.
Not every type of well water is suitable for pond water. This is the reason that a lot of wells are NOT used to source of drinking water. In agricultural regions herbicides (weed killers), pesticides (pest control agents), fertilisers (phosphate and nitrate), as well as some very high iron concentrations can accumulate in the groundwater (= well water). You can check phosphate, nitrate and iron contents reliably and quickly with water tests. Herbicides and fungicides are difficult to trace. Please test your well water in a mini aquarium with plants and microorganisms (not with fish!) before using it in the pond. This will quickly and clearly show whether it is suitable for the pond.