O_O where is your boy friend getting his information? PH is the acidity or alkinity of the water, how long it stays in the tank (unless you have something in there that lowers the ph) should not change the ph. If he hasn't joined here yet, I suggest you get him over here... we have correct info! XD
this is cycling :) Unfortunately it's pretty much impossible to get a stable and reliable cycle in anything less than say a 5 gallon, though that's not bad per say.
You could divide and cycle a ten gallon. That way you only have to have one filter, and one heater and one tank, and you can still fufil the needs of each fish. Petsmart (I think) is still having a sale on empty 10 gallon tanks for 12 dollars. You can find a good filter for maybe 15-20 ish dollars (I highly recommend Aquaclear 20 for a 10 gallon), and a good heater for 20 ish dollars (Aqueon 50watt Pro would work well in a 10 gallon).