i just tested my 2 10G and my 20G and my 30G for ph and ammounia and i dunno what a good number is for each one? i would think in the middle of the chart but i dunno im kinda new when it comes to testing and everything
or making sure that there are enough of the "good bacteria" to get rid of the ammonia your fish produce i forget what these are called but im pretty sure the name is not as important as what they do. Just as long as there is ammonia in the tank these bacteria will eventually set up a colony nand everything should eventually level itselff out. Before that though then water changes would be the only way to remove ammonia from the water.
There are things out there that will lock up or neutralize ammonia or something but it still has to be removed and for that reason i say nothing beats a good old fashioned water change.
Don't worry to much about ph unless it is above 9.5 or below 6.
Just try and avoid quick,big swings in pH Most fish handle temprature and Ph swings pretty good if they are slow and steady.