One week is not enough time to cycle a tank. Your tank needs to build up a bio filter of nitrifying bacteria in order to sustain the fish you put into it and have them and the tank be healthy. During this cycle your tank will go through high spikes of toxic amonia and nitrite that can kill and will definately affect the health of your fish in the long run, if they do live through the cycle. Once you get your tank up and running, you'll need a master test kit to test for amonia, nitrite, and nitrates. You'll also want a ph test kit as you'll need to maintain you rph at a stable reading.
You can use fish food, pure amonia (with no detergents), or dark brown sugar to seed the tank. This is "fishless cycling" and is the most recomended method rather than subjecting fish to the toxin levels of a cycling tank. You add a bit each day and test the water every few days. (I wouldn't test for the first week since you'll probably get no readings at that point) The first thing you'll see is an amonia reading...this will range from low readings of .25 an may gradually get very high. Once you have amonia, you should do a 30% water change. I do more like 50% at this point....but that's just me. soon after you start seeing amonia, you'll also start getting readings of Nitrites. After the first water change I do water changes every couple days of about 30%. You'll soon start seeing Nitrates in your tank. Once your levels are 0 amonia, 0 nitrite, and you have nitrate readings along with those 0 readings, your tank is cycled. But, continue doing water changes till you nitrate levels are below 30 ppm. While nitrates are not as toic to fish as Nitrites and Amonia, they are still toxic to fish at high levels. Once you have lowered your Nitrates, you're ready to add fish. But then you want to add them slowly. Maybe two at a time. The bacteria need to adjust and multiply to the demand of the waste your fish produce.
The whole process can take anywhere from 2 weeks to 6 weeks. Seems like a long time to have no fish in your tank, but it's a good way to avoid all the problems that can arrise from not properly cycling a tank, like diseses such as ich.
You can also cycle with fish....but that exposes the fish to the high levels of amonia and nitrites your tank will go through and while the heartiest of fish my live through it, it can greatly affect their health an immunity to diseases in the long run.