David,
Keep watching the ammonia, nitrite and nitrate levels. It sounds like you may be coming to the end of the cylce or you may have done something that will cause it to do another cycle all over again. From what I gather chemicals are not very stable compared to just letting it cycle on its own. Speeding up the process sometimes just amkes the system unstable instead of doing what it says it does on the package. If your ammonia stays at .25 or below and your nitrates do not go up in the next week or so and your nitrites stay at or below 10 you may be ok. Its a little shakey becuase like I said the chemicals may be unstable and show wierd numbers. A number of 10 or less perferably 0 on the nitrates is acceptable. the ammonia and the nitrites really need to be at 0. The .25 that you are reading should turn into nitirites shortly if your bacteria is building correctly.
This is the best possible advice that we can give you. You just have to be patient like the rest of us. If you throw fish in there just because you want to they will likely die and then you will have a new ammonia problem beacuse of the dead fish and the whole cycle wills tart over again. ammonia and nitrites are extremely toxic to fish. We are not trying to single you out or anything, we just like to see people get to a point where they can be proud to have a nice established tank that is being taken care of and the livestock is afforded a little time and effort towards thier health.
As far as your question concerning the bio balls, im afraid i don't know much about them, Im sure if you present a possitive additude towards seting your tank up responsibly that someone who knows will come along and give you some more sound advice.