kdodds wrote:Simple aquarium dechlorinator will remove chlorine, but not chloramine, which most municipalities now use as it is more stable than chlorine. Luckily (for aquarists anyway) most chlorine removal products now also render chloramine inert. I do not, however, know if these products will introduce chemicals harmful to plants or bonsais specifically, but I can say that aquatic gardeners use them with great success.
I don't see why you can't use a dechlorinator if chlorine is a problem. I use it for my aquarium which is extremely successful it also has aquatic plants that are not effected by it. I will add that if you read the instructions in any tap water conditioning product it says a small amount will remove chlorine. If you increase the dose stated on the second part of the instructions then it will remove chloramines as well. My tapwater has chlorine and chloramines but my tree is thriving. Unsure on what level there is in it though.
If there's that much worry about the water supply, a simple carbon filter might help. If not, there's always distilled water, or RO water from your local aquarium shop, which is usually less than a dollar per gallon and virtually pure. The problem with either is that there are NO minerals, electrolytes, etc. and either will tend to take up minerals and elements from the soil quite readily, perhaps depleting the soil rapidly. You'd really have to ask someone with more experience about that, though. I just use plain old tap water, always have.
With RO water you are quite correct it takes literally everything out! RO water is mostly used for marine aquariums but the vital minerals need to be readded to the water before use and they come in powder form which most aquatic shops sell (as long as they have marine fish, equipment etc.) So that is a possibility you can also buy equipment that can turn normal water into RO water. The thing is though what this piece of equipment does is remove all the impurities which is seperated and its full of nitrates as it gets more concentrated along with the other stuff. Because of this it is apparently very good for plants so this particular marine specialist shop told me when I enquired. On that info I doubt nitrates would have an adverse effect on plants. My tapwater has roughly 20mg of nitrates in it thats 20ppm (parts per million) which is a totally acceptable level. If you want to test your water for nitrates then simply buy a nitrate testing kit which are fairly inexpensive from any pet stores that deal with fish.
That last part was for the thought that the nitrates make the leaves yellow because of high nitrate levels in this thread.