Honestly, IMO I would not touch anything while your tank is cycling. That is what a cycle is basically for. Your levels will go up and down. This is normal. My tank cycled for over 3 weeks before all of the levels went down to 0. As far as phosphates are concerned. I would definately buy RO/DI water as opposed to using regular tap water. You may even invest in an RO/DI filtration system to save yourself some bucks down the road. they are a little costly, but if you have the $$ now eventually, it will pay off down the road. Also, I reccomend doing a 25% water change every month. I usually do 10% per week. This will also help in aiding keeping your water levels low. I would not start to do this until after the cycling has been completed though. Hope this helps some!
Sheppie