Though from whence one gets their tap water and its quality may not seem to be on-topic; I believe it dramatically effects your tanks water quality and, especially the livestock which is taken from the wild.
If you are feeling safe in knowing that reverse osmosis removes contaminations from the water, think about this:
Emerging contaminates range from gasoline additives which enter the water supply from run off, to estrogen tablets taken as a birth control method. Reverse osmosis can only remove particles which are larger than a water molecule. There are many chemical molecules which are smaller than a water molecule, including medications which are released into urban waste water systems from the human urinary tract! Think of it, Prozac, Viagra, and the human hormone Estrogen, just to name a few, may be smaller than a water molecule.
In regions of plentiful water, sewage is often treated, then discarded into bodies of water where fish live and breed. In nearly all of the Western United States, there is an old saying that, "Whiskey is for drinking and Water is for fighting over." Water is rare enough that potable municipal water is recycled from raw sewage. The system is often referred to as "Crap to Tap."
The following is an article taken last spring from an Arizona newspaper article:
Treated Wastewater Harmful to Fish, Could be Harmful to People
A study conducted recently by University of Arizona scientists suggests that prolonged exposure or consumption of potable water derived from treated wastewater could cause detrimental health effects.
In the study, researchers placed an endangered fish species Ã¢â‚¬â€ the bonytail chub Ã¢â‚¬â€ in tanks that contained, in part, treated effluent from Pima CountyÃ¢â‚¬â„¢s Roger Road sewage plant.
After three months, the fish began to show up to five times more hormones of the opposite sex than their own sex, effectively altering their sexuality. Other studies in the United States and Europe have resulted in similar findings.
The researchers told the Arizona Daily Star that they worry it is not just fish that could be affected. No one knows if the compounds in treated wastewater can harm human reproduction because their effects on people havenÃ¢â‚¬â„¢t been studied thoroughly, the scientists say. Tucson residents may want this information within the next few years; they are expected to determine by 2014 if they want Tucson Water officials to begin a so-called Ã¢â‚¬Å“toilet-to-tapÃ¢â‚¬Â program.