You want to match the water conditions as close as possible. pH and temp are biggies. You should only do 25% every week...50% at the most. I think that for cycling, you might be ok if it was established. However if the water in your tap is cholorinated, then you need the conditioner to remove it (and other stuff), and the cholrine probably was killing the bacteria to make the tank healthy and stable.
I kept a betta for a good year, before I knew how to do it properly, with chlorinated aweful water. though I think I let the water sit and the chlorine evaporates out. You still need conditioner for chloramine which doesn't. But you should be able to save what you have.
there are stickies about cycling- read them!! (also is you internet search this, you'll find a lot of info, I found some stickeys to be vague, though I didn't read them so closely) Cycling is a fairly dangerous process to do with fish, but they can survive as long as you test the water (aquapharm test kit with mulitple tests for ammonia, nitrite ,nitrate, and pH is what i'd recommend,don't be intimidated by all the test tubes!) and keep toxins like ammonia down with water changes, you might fair well.
