Whatever you do, don't get any more fish or over feed. :(  Several of us have prevailed through worse situations. :)

If your tap water is very hard, that means it has a lot of minerals or "mineral salts" in it like calcium, magnesium and maybe iron. At a certain level, those can be fatal, even to a hardwater fish like guppies. So DJ's and miskairal's suggestions about a couple of partial water changes a week are spot on, both to dilute the mineral content and even more importantly to dilute the nitrogenous toxins,.

Did you test the tap water and the bottled water and make comparisons?  What did they measure out as?

By the way. curing the water with a water conditioner means that the chlorine is forced out of the water because of an interesting reaction to Sodium Thiosulfate. The possible ammonia in your water is temporarily chemically bonded to a substance suspiciously like formalin or a formaldehyde derivative. It will bubble loose in a few days or weeks, which is another reason we want to get your tank's cycling process on its way.  There are also substances in there which will bond heavy metals such as copper from your pipes, lead from your municipal pipes, and maybe even the aluminum sulfate (alum!) many of our water departments are putting into are water supplies to keep the pH up so more of the lead pipes don't dissolve.

Those don't do anything about getting the over abundance of carbon dioxide (CO2) and free nitrogen (which can form the bubbles on the sides of tanks or water holding containers) in the water and allow a little free oxygen to settle into the water (much to the delight of out guppies). Putting an airstone in there may help too. All that is why we need to let the water sit a few days *

Several holding containers, all sort of food quality plastic, gallon water jug or very clean (soap-less, usually hot water soaked milk bottles with the top off), the better garbage cans never used for garbage, those food quality 50-gallon drums and all sorts of plastic storage containers or, maybe best of all, those five-gallon clear water bottles from office water coolers (available from the guys who drive the trucks and all sorts of re-sale stores) can be used for that process. Either locating those containers where it is warm (or if you are an over-achiever) sitting them on pieces of styrofoam and putting a high power submersible aquarium heater in them will prepare the water for water changes.

Bottled water, most, perhaps all of the time, is basically rebuilt R.O. water with healthful additions of calcium-something-or-other, magnesium-something-or-other and (for flavor) a set portion of potassium-something-or-other. Look at the ingredients label. It probably is somewhat hard, but not as hard as your tap water.

I was started when a neighbor purchased one of those Betta vases. The instructions said to use bottled water. Presumably there is no chlorine, ammonia, ammonia, CO2, alum or the other bad stuff in there. Also, I wouldn't be surprised to find that it was aerated a little, though I couldn't prove it. (I do know a bottler though and could call him.) The people promoting the Betta bowl must have figured that a couple water bottled a week was affordable. They also must figured that a lot trouble with the tap water could be avoided.

Thinking about your questions, I swung by the beverage section at a local drug store, while running errands. The gallon bottles of water cost between a dollar (U.S.) and about $1.45. Three to five of those is a lot of money to just to do partial water changes on a ten-gallon tank. So you would probably be able to do those changes for a period of time and lower the tank's hardness. It might be cheaper to buy one or two bottles of RO or distilled or DI (deionized) water and mix that in with your tap water. Depending upon your I would recommend 1 gallon of the demineralized water per 3 gallons of your tap water.

However if your tap water hardness is only 200PPM or about 13 DH (Degrees Hardness), I would just go with it. Far more important is whether you are doing partial weekly water changes with water which is seasoned one way or the other. Especially in the winter, if you are not doing these changes, it does matter in the long run whether your are adjusting your water's hardness. Your fish will eventually slow down, suffocate and die of nitrogen poisoning.

If your tank is not showing any ammonia reading, but is already showing a spike of nitrates already, the process is going along. In time there should be a rise of nitrites and a drop in nitrate readings. What we all hope for are readings which show no ammonia or nitrates and a safe amount of nitrites. A test kit here suggests under 1PPM nitrite is ok, above it is not. An on-line source suggested one should realistically aim for under 25 PPM of nitrite.

Your pH is a little high. The higher the pH, the more dangerous is ammonia, et al. That just means (oh no, he's going to say it again!) keep changing the water. ;)

However, as fish pass waste products, as the bacteria cycle these products, those biological processes will drop your pH a little. That is better than messing around with chemicals to drop the pH.

Alkalinity is the measure of substances, often carbonates, which buffer your pH (up). Baking soda is an example of such a substance. You can have a high pH, yet fair low Alkalinity measures. In such a situation if the water gets diluted with demineralized water or if the fish are actively dumping waste products into the water, the pH will drop. If there is a low K reading, the pH will drop faster.

I wish that more shops would tell their new customers about fish-less cycling. A lot of info is becoming available on the Net. For a bit more see
http://www.thetropicaltank.co.uk/bcycling.htm
http://www.thetropicaltank.co.uk/cycling2.htm

Would you see if you can get soap-less, clean (not oily) containers so that you can really hold on to some water for a few days before water changes? Right now, that is one of the most important things you can do for your fishes.

You may just be able to hot water soak and blast out gallon milk jugs. Drinking water gallon jug (or the 3 gallon ones) are easier to prepare. Just drink the water. ;)  And store them out of the sun.

Of course, there are all sorts of fancy water holders available through home brew places and/or lab supply places. But wow, are they expensive! Even Rubbermaid 7-gal. Water Cooler (for campers) are expensive!

The five-gallon water cooler bottles are surprisingly expensive. Of course I snagged two last summer for a dollar each through a garage sale and a re-sale shop.

All the best!
uncle (still not a chemist) scott