You should be able to get this information from your municipal water department. If yours is an American community, they should have a copy of their EPA statement. Sometimes the report on hand is less than that, but still should be revealing.

Ah! This is well water at your farm! Have you even  had a water analysis done on your well water? I would think that would have been done (sometime) for the benefit of your animals and your family. (Or is that for your family and livestock?)

If it is a whole lot harder than 170 or 180 PPM, than yes you need to cut it with some sort of demineralized water such as rain/ R.O. /the very expensive distilled/ or stuff run through an ion exchange. R.O. is usually the easiest to produce.

Don't use straight R.O. In almost all cases that will kill the fish. If your hardness was 240 PPM, then in a holding container, mix 50% tap water and 50% R,O. or 60/40. GRADUALLY add that to your tanks (airline siphons are good) so that your fish don't undergo osmotic shock, where grim things like hemorrhaging gills take place. (That can be a cause of the ever popular mystery deaths in a tank.)

See also Winter Mystery Deaths
http://www.guppylog.com/story/2004/2/7/73527/94333

By the way, FancyGuppyGuy, don't confuse pH with hardness. They are measures of different things, caused by different substances. While it is true that the minerals buffering pH at a high level are often found with the minerals raising hardness, that is not always the case. In Arizona, I know of a guy whose tap water is a pH of over 9. His hardness is under 60 PPM !

A old, unchanged aquarium, with lots of evaporation, may have so many biological processes going that it has a relatively low pH, yet have a huge DH or hardness. And the TDS (total dissolved solids) may be off the chart. Google Guppylog and TDS for more on that.

When your tap water rose from 7.4 to 8.0 with aeration, it is probable that your were knocking a lot of the carbon dioxide out of the tap water. That is good for your fish, in that tap water may have little free oxygen and too much CO2.

wwtinksk9, your water softener will actually increase TDS in a tank. When it exchanges sodium chloride for hardness salts it puts in 2 sodium molecules for every molecule of calcium or magnesium it takes out. Some of that water is fine for guppies, though their naturally waters will usually have a lot more calcium and magnesium than sodium in it. It may be hard on some plants and make softwater fishes hard to breed.

Evidentally sodium water is easier on RO membranes than calcium and magnesium, so if you are using your RO unit, it is better to use the softened water for that. The RO unit will be more efficient and last longer.

Remember that when homes are equipped with water softeners, the water softeners may be hooked up just to the hot water. It is recommended that we drink and cook with the water from the cold water tap. Unless alterations need to be made for our fishes, it sounds like the tap water would be best for them.

It sounds like there is also a supply issue. A couple of camping water carboys might be useful. (Check K-mart camping sections.) If the distances were shorter I would suggest using drinking quality (or well washed out) hoses, maybe attached to a portable sump pump. If you Google for [aquariums water pumps] [water changes pumps] or [automatic aquarium water changers] you should be able to find a lot of material on that.

In a general sense, what part of the country are you from? Members of a fish club, garden club or pond supplier might be able to help.

Hope this is useful grist for the mill. More importantly, hope your water (with some "seasoning") fits guppies now. :)