"Fishy" cycling

Here's a chart of the water quality in my 20 gallon tall aquarium. I'm starting to cycle the tank with six 1" tiger barbs. My concerns are that the ammonia level is still high after a water change on 12/8/2007. I did a 2.5 gallon water change (gravel was vacuumed), and treated the water with five drops of Prime (added to the bucket before being filled with fresh water). I am also concerned that my water is high on the alkaline side (7.8), as I have read that ammonia is much more dangerous when the water is alkaline.

Should I perform another small water change? I've also read that when establishing the bacteria in the tank, you want to keep the water changes smaller because you can end up removing the bacteria from the tank with each change. Is that correct? Or is the ammonia a serious enough issue to warrant a 5 gallon (25%) water change?

Edit: I also want to mention that the water temperature is kept at 75 F. I was also wondering if a higher temperature would promote faster bacteria growth.

I just performed a 50% water change. Ammonia is back down to 0 mg/L. I will test again tomorrow, and if the water is unacceptable, perform another water change.

Ammonia readings for my tap water are 0 mg/L.

I will cut the feedings back to every other day as SM suggested, and perform enough water changes to keep the ammonia below .25 mg/L..

Oddly, I can no longer edit my original post. I wanted to change the url of the chart to a permalink, but I'll display it in this post instead. This chart will update as I input new data. As you can see, the ammonia level is down to .5 mg/L, and that is after another 50% water change this evening.



Should I do another 50% change now? That would leave 25% of the water from yesterday in the tank. I'm a bit leary of doing so at this hour, but I suppose I should if I need to get the ammonia level down to less than .25 mg/L.